nuclear physics news · nuclear physics news volume 18/no. 4 vol. 18, no. 4, 2008, nuclear physics...

Nuclear Physics NewsVolume 18/No. 4

Vol. 18, No. 4, 2008, Nuclear Physics News 1

Nuclear Physics News is published on behalf of the Nuclear Physics European Collaboration Committee (NuPECC), an Expert Committee of the EuropeanScience Foundation, with colleagues from Europe, America, and Asia.

Editor: Gabriele-Elisabeth Körner

Editorial BoardT. Bressani, Torino S. Nagamiya, TsukubaR. F. Casten, Yale A. Shotter, VancouverP.-H. Heenen, Brussels (Chairman) H. Ströher, JülichJ. Kvasil, Prague T. J. Symons, BerkeleyM. Lewitowicz, Caen C. Trautmann, Darmstadt

Editorial Office: Physikdepartment, E12, Technische Universitat München, 85748 Garching, Germany, Tel: +49 89 2891 2293, +49 172 89 15011, Fax: +49 89 2891 2298,

E-mail: [email protected]

CorrespondentsArgentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Leeb, Vienna; Belgium:G. Neyens, Leuven; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou,TRIUMF; K, Sharma, Manitoba; C. Svensson, Guelph: China: W. Zhan, Lanzhou; Croatia: R. Caplar, Zagreb; CzechRepublic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Århus; Finland: M. Leino,Jyväskylä; France: G. De France, GANIL Caen; M. MacCormick, IPN Orsay; Germany: K. Langanke, GSI Darmstadt;U. Wiedner, Bochum; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen; India: D. K. Avasthi, NewDelhi; Israel: N. Auerbach, Tel Aviv; Italy: M. Ripani, Genova; L. Corradi, Legnaro; Japan: T. Motobayashi, RIKEN;Mexico: J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen,Bergen; Poland: B. Fornal, Cracow; Portugal: M. Fernanda Silva, Sacavém; Romania: V. Zamfir, Bucharest;Russia: Yu. Novikov, St. Petersburg; Serbia: S. Jokic, Belgrade; South Africa: S. Mullins, Cape Town; Spain:B. Rubio, Valencia; Sweden: J. Nyberg, Uppsala; Switzerland: K. Kirch, PSI Villigen; United Kingdom: P. Regan,Surrey; USA: D. Geesaman, Argonne; D. W. Higinbotham, Jefferson Lab; M. Thoenessen, Michigan State Univ.; H. G. Ritter,Lawrence Berkeley Laboratory; G. Miller, Seattle.

Copyright © 2008 Taylor & Francis Group, LLC. Reproduction without permission is prohibited.All rights reserved. The opinions expressed in NPN are not necessarily those of the editors or publishers.

Nuclear Physics News ISSN 1050-6896

Advertising Manager Maureen M. Williams, 28014 N. 123rd Lane, Peoria, AZ 85383, USATel: +1 623 544 1698Fax: +1 623 544 1699E-mail: [email protected]

Circulation and SubscriptionsTaylor & Francis Inc.325 Chestnut Street8th FloorPhiladelphia, PA 19106, USATel: +1 215 625 8900Fax: +1 215 625 8914

SubscriptionsNuclear Physics News is supplied free of charge to nuclear physicists from contributing countries upon request. In addition, the following subscriptions are available:

Volume 18 (2008), 4 issues Personal: $93 USD, £55 GBP, €74 EuroInstitution: $768 USD, £465 GBP, €614 Euro

NuclearPhysics

News

2 Nuclear Physics News, Vol. 18, No. 4, 2008

Cover illustration:

Volume 18/No. 4

Contents

Editorial .............................................................................................................................................................. 3

Laboratory PortraitThe Nuclear Physics Laboratory at CEA DAM Ile-de-France

by Eric Bauge .................................................................................................................................................. 5

Feature ArticleDeep Underground Laboratories—Somewhere Quiet in the Universe

by Neil Spooner ............................................................................................................................................. 13

Facilities and MethodsJUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei

by David J. Dean ........................................................................................................................................... 21

Compass and the Nucleon Spin Puzzleby Bradamante............................................................................................................................................... 26

Impact and ApplicationsIndustrial PET at Birmingham

by David Parker ............................................................................................................................................. 33

Meeting ReportsThe 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13

by Kris Heyde ................................................................................................................................................. 37

Hadron Physics Summer School 2008by Frank Goldenbaum .................................................................................................................................... 38

News and Views ................................................................................................................................................ 40

Calendar ............................................................................................................................................................ 44

editorial


The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

OECD Global Science Forum Report on Nuclear Physics

Globally about $2B is spent annu-ally for Nuclear Physics research.Over 13,000 scientists, engineers,and students involved in research car-ried out primarily at the 90 majoraccelerator facilities with user pro-grams, but also at a range of smaller,specialized facilities that provide fornational needs. This is a truly enor-mous human endeavor and it issobering to think that our science jus-tifies such a commitment ofresources.

This rather startling insight is oneof a number of interesting resultsfrom the efforts of the WorkingGroup on Nuclear Physics, estab-lished by the Global Science Forumof the OECD (Organisation for Eco-nomic Co-operation and Develop-ment). Their report was publishedearlier this year and can be accessedat www.oecd.org/sti/gsf.

The Global Science Forum pro-vides a venue for communicationbetween senior science policy offi-cials and the Forum’s activities pro-duce findings and recommendationsfor action by governments, interna-tional organizations, and the scien-tific community. The last report onNuclear Physics was by the WorkingGroup on Nuclear Physics (1996–1999) chaired by Bernard Frois andhighlighted the enormous potentialthat the development of radioactivebeam facilities would provide fornuclear physics research. That reportprovided the background for the lastround of large-scale investment inour field. The present WorkingGroup was established in 2006 and

was chaired by Dennis Kovar. Its rec-ommendations set the backdropagainst which the funding agencieswill plan investment in our field forthe next decade.

The report draws attention to themajor advances that have occurred inthe decade since the last report waspublished, highlighting of particularinterest: the observation of a newstate of matter in the form of theQGP, the confirmation from solarneutrino measurements that neutrinoshave mass, and the explosion ofknowledge regarding exotic nuclearstructure and nuclear astrophysicsmade possible by the advent of radio-active beam facilities. The workinggroup assessment for the next decadeis equally bright, with the main chal-lenges summarized in a series ofquestions: Is QCD the complete the-ory of the strong interaction? Whatare the phases of nuclear matter?What is the structure of nuclear mat-ter? What is the role of nuclei inshaping the evolution of the uni-verse? What physics is there beyondthe standard model?

The section of the report that willperhaps be of most interest to ourfunding agencies (and so impactdirectly on our ambitions as scientists)relates to international cooperationand strategic planning. The workinggroup observes that internationalcooperation has long been the norm inour science and as evidence for thisnotes the large external user presenceat major national facilities (for exam-ple GSI 40%, RHIC 50%, CEBAF40%, and TRIUMF 66%). The report

strongly endorses this international-ization of our science and recom-mends that “free and open access tobeam usage should continue to be theinternational mode of operation fornuclear physics facilities.” The reportalso notes that our community haseffectively developed a worldwideroadmap for the development of thesubject. Particularly important in thisregard are the periodic Long RangePlans prepared in Europe by NuPECC(www.nupecc.org/pubs/lrp03/long_range_plan_2004.pdf) and in theUnited States by NSAC (www.sc.doe.gov/np/nsac/nsac.html). The reportfinds that “this global roadmapreflects a high degree of coordinationin optimizing the available resourcesfor the world-wide nuclear physicsprogramme.” The working groupsuggests that a mechanism should beestablished to review this globalroadmap on a regular basis and pro-poses that WG9, the IUPAP WorkingGroup on Nuclear Physics, mighttake on this role.

As noted earlier, these periodicOECD reports do exert influenceover the direction in which our fielddevelops, because they are reportscommissioned by, and accepted by,our funding agencies. For this reasonthey form valuable reading for theresearch community. Indeed, thepresent report has already hadnoticeable effects. Colleagues inAsia have recognized the benefits ofregional planning and are in theprocess of establishing a version ofNuPECC that will allow Asiancountries to extend cooperation and

editorial


develop regional plans, and WG9 hasalready discussed the proposal thatthey take on the role of preparingand updating a global roadmap forthe field based on the regional plan-ning. Such moves are timely, forwhile our field is currently at a stagewhere the scale of facilities can beaccommodated on a regional basis,some of the ambitious plans that areemerging (e.g., for Electron IonColliders or next generation ISOLfacilities) may need to be consideredon a world basis.

DENNIS KOVAR

DOE Former Associate Directorof Science for Nuclear Physics

BRIAN FULTON

NuPECC Chair

laboratory portrait


The Nuclear Physics Laboratory at CEA DAM Ile-de-France

Introduction The Nuclear Physics Laboratory

(Service de Physique Nucléaire, SPN)belongs to the Military ApplicationDivision (Direction des Applicationsmilitaries, DAM) of the FrenchAtomic Energy Commission (Com-missariat à l’Energie Atomique,CEA). It is located in the DIF (DAMIle de France) research center inBruyères-le-Châtel, 30km south of Paris.

The laboratory houses 44 staffmembers, plus several PhD students,post docs, and foreign visitors. Its pro-grams range from support to the DAMSimulation program, to fundamentalexperimental and theoretical nuclearphysics studies. The originality ofSPN actually resides in that continu-ous coverage of the whole spectrum ofnuclear physics from fundamentalstudies to applied physics.

Since its creation, almost 50 yearsago, most of the scientific activities,especially the experimental ones,involve the neutron; either as an incom-ing or an outgoing particle, and many(n,γ), (n,n’), (n,xn), or (n,f) cross-sec-tions have been measured in Bruyères-le-Châtel. Theoretical studies were alsoinitiated long ago in the domains ofnucleon–nucleus reactions and micro-scopic nuclear structure theory.

Today, the programs carried out inSPN can be roughly grouped into fourmain research directions:

• Theoretical studies of the nuclearmany-body problem with applica-tions to both nuclear structure andnuclear reactions.

• Experimental and theoretical stud-ies of the fission phenomenon.

• Studies on short-lived nuclear statesor isomers, including their interac-tions with laser-induced plasmas.

• Nuclear data for applications andtheir covariances.

Naturally, these four topics exhibit someoverlap. For example, fission studieshave a strong impact on nuclear dataworks, or the many-body calculations ofnuclear structure produce results that arefurther used in fission, isomer, ornuclear data studies. Actually, that over-lap between topics is a clear manifesta-tion of the complementarities and stronginteractions between the SPN physicists.

Nevertheless, those internal com-plementarities do not preclude collab-orations, as evidenced by our stronginvolvement in many national andinternational collaborative efforts.

Before going into each of the fourmain topics, the present article shallfirst detail our on-site experimentalfacilities as well as our current arrayof detection systems.

Facilities Besides the aforementioned four

main research topics, SPN also oper-ates a KN4000 4 MV Van de Graaffelectrostatic accelerator facility forapplications like measurement of neu-tron cross-sections, neutron or gammadetector calibrations, and chemicalanalysis of matter using ion beams.That facility is used in support ofmany of the experimental studies pur-sued at SPN.

The 4 MV Van de Graaff is anHVEE-electrostatic accelerator thatdelivers 1H+, 2H+, 3He+, and 4He+ ionswithin the energy range 420 keV to

4 MeV. Possible Xe+ ions beam wasadded in the eighties on a specificbeam-line. Pulsed or continuous ionbeams are available. In pulsed mode,the repetition rate is fixed at 2.5 MHz(400 ns) and the FWHM is about 10ns.Attached to that accelerator are fivebeam-lines serving the two experimen-tal rooms. One of these beam-lines isdedicated to the neutron productionwith a Mobley buncher (to reduce theFWHM of the pulsed beam to 1–2 ns),a capacitive beam pick-off detector (tomeasure that FWHM) and two NE213and BF3 detectors, to monitor the neu-tron flux on-line. Mono-energetic neu-trons are created by nuclear reactionsbetween the accelerated 1H+, 2H+ ions,with thin layer of lithium, or deute-rium, or tritium-loaded Ti. Neutronenergy is defined by the specific reac-tions and by choosing the appropriateangle. The range of energy is 30 keVto 20 MeV and the neutron emissionrate is of the order of 107 n/s/sr.

That accelerator is shared in theEFNUDAT [1], 6th Framework Euro-pean program for encouraging transna-tional access to nuclear physicsinfrastructure among member countries.

SPN is also strongly involved in theproject of the future NFS (Neutron ForScience) neutron source that should beconstructed as a part of the SPIRAL2facility in GANIL (Caen, France) in theyear 2012. That NFS neutron sourcewill deliver neutrons in a continuousspectrum peaking near 20 MeV withintensities much stronger than that ofthe other European facilities (Gelina,nTOF) in that energy range.

Finally, for theoretical studies,computing facilities constitute the

laboratory portrait


counterpart to experimental facilities.CEA DAM Ile-de-France hosts twohigh-performance computing centers,CCRT and TERA, which allow us todevelop ambitious theoretical programsthat require large amounts of computingpower.

Detection Systems SPN currently operates three major

detector systems. The CARMEN detector (Cells

Arrangement Relative to the Measure-ment of Neutrons) [2] is a large organicscintillator tank-type detector devoted toneutron counting. It is the continuationof a long SPN tradition since the firstneutron counting ball was built in 1964by M. Soleilhac. CARMEN consists oftwo independent vertical hemispheres,each one equipped with 12 photomulti-pliers. The active part which is a gado-linium-loaded scintillating organicliquid (BC521) has a total volume of1m3. Like in many detectors of thistype, neutrons are moderated in theorganic liquid before being captured

mainly by the Gd nuclei. In the case ofCARMEN, the neutron detection isspread over the 50μs following thenuclear reaction (99% of the neutronsare captured at that time). This timespreading allows for counting neutronseven for high-multiplicity events. Hencethis detector is adequate for (n,xn) mea-surements. CARMEN is a high-efficiency detector (85% efficiency for252Cf fission neutrons). Moreover, thedistance between the two hemispherescan be adjusted according to the experi-ment’s needs. This peculiarity allowsmeasurements of neutron spectra corre-lated to neutron multiplicity.

Since the beginning of 2008, wehave been developing a 3He based neu-tron counter. It consists of a50*50*75cm3 polyethylene block with23 inserted 10 bars 3He proportionalcounters. This device works similarly toCARMEN: neutrons are first moderatedin polyethylene before reacting with the3He counters. It is nevertheless com-pletely insensible to gamma rays. It alsopossesses an external shielding (10cm

of polyethylene and 4mm of innerboron carbide). Its detection efficiencyis 50% from fission neutron from 252Cf.Although this detector is mainly acounter, it is able to provide a rough esti-mate of neutron spectra. Such an instru-ment can be used for fission studies and(n,xn) reaction measurements.

The Lead Slowing Down Spectrom-eter (LSDS) installed on the WNR neu-tron source at the Los Alamos NationalLaboratory (USA) was first operated inBruyères-le-Châtel as the CIRENEassembly. At that time, it was devoted toisomeric ratio measurements in the reso-nance region. Its installation at the WNRintense source gives the opportunity tomeasure cross-sections on very smallmatter quantities (down to 10ng), or tomeasure very small cross-sections forneutron energies ranging from 0.1eV to100keV. That method was first demon-strated in 1955 [3]. It profits from thegreat probability for neutrons to scatterelastically in natural lead, and from thevery strong time/energy correlationwithin the cube. The gradual slowing ofneutrons in the cube produces a gain inapparent neutron flux of the order of 103

compared to usual time of flight bases.In this way the useful neutron flux onthe LSDS at Los Alamos can be as highas 4.1010 n/cm2/s.

Theoretical Nuclear Many-Body Problem

The theoretical treatment ofnuclear structure with mean-field-based approaches has long been aspecificity of our laboratory. The her-itage of pioneering works of DanielGogny on the effective nuclear inter-action [4] and its use within theframeworks of mean-field [5] andbeyond-the-mean-field theories is stillliving. Those theories constitute abase on which are built modern funda-mental developments. These theories

Figure 1. The 4 MV Van de Graaff electrostatic accelerator of SPN (open withthe visible glowing ion source).

Q1

laboratory portrait


exhibit a strong predictive power thatcan be challenged by experimental datalike mass or nuclear spectroscopy ofstable and unstable nuclei. The currentthrust in those studies consists in usingthe Gogny interaction in approachesthat include more and more correla-tions beyond the single-particle pictureof the mean field approximation. Suchapproaches are for example Quasi-Particle Random Phase Approximation(QRPA) [6], multi-particle multi-holeconfiguration mixing [7], or GeneratorCoordinate Method (GCM) [8]. Thenuclear properties predicted within thesetheoretical frameworks are then com-pared with the latest experimental dataon unstable nuclei, allowing us to con-tribute to the fundamental understandingof nuclear stability, the persistence orerosion of (sub-)shell gaps far from thebeta stability line, giant resonances, andnuclear shape coexistence [9].

Another theme of study consists inlarge-scale systematic calculations ofnuclear properties, which provide awealth of results that can be exploited toget a better picture of the global evolu-tion of nuclear properties across thechart of nuclei [10]. These studies aremade possible by the availability ofmassive amounts of computing powerat the CCRT and TERA computingcenters. Our website (http://www-phynu.cea.fr) presents extensive calcu-lations of the stable and unstable nucleias they are predicted, from drip-line todrip-line, within axially symmetric Har-tree-Fock-Bogoliubov (HFB) frame-work using the Gogny D1S interaction.

The D1S interaction itself is pres-ently under review, and severalimprovements to that interaction arecurrently investigated [11].

Another trend in the nuclear many-body problem is the convergence ofstructure and reaction studies. A firstexample of such a convergence is the

use of approaches based on HFB andcollective dynamics for fission studies.Another example resides in the growinguse of ingredients derived from theoret-ical nuclear structure studies in reactionmodels, such as level densities derivedfrom single particle levels or nuclearmatter radial densities in finite nuclei.These will be discussed in the sectionon “nuclear reaction modeling.”

Fission SPN has been involved in the study

of fission for many years. The worksby Fréhaut and collaborators about30 years ago on fission neutron multi-plicity measurements from the reso-nance region up to 28MeV are still abasic reference [12]. In the field of the-ory, the pioneering work of Berger etal.was the first to achieve a microscopicdescription of the scission of fissioningsystems, as well as the transition fromfission to the fusion valley [13].

Today, nuclear fission is one of themain research fields in SPN. The

approach is triple: experiments, theoryand nuclear data evaluation.

Experimental Fission Studies A program for measuring fission

neutron energy spectrum and multiplic-ity in neutron-induced fission in the1–200 MeV range has been initiated atthe Los Alamos Neutron Science Center(LANSCE). This work provides unprec-edented data for 238U, 235U, and 237Np[14], the interpretation of which is per-formed in conjunction with the theorists.More complex experiments includingfission fragment mass measurements areforeseen. Fission is also studied on thespallation-driven LSDS.

The group is also at the origin of anovel experimental project to be per-formed at the ELISE Electron–ioncollider to be constructed at FAIR thefuture facility at GSI, Darmstadt. Thegoal of this reverse kinematics experi-ment is to measure event by event themain fission observables with anunprecedented precision: unambiguous

Figure 2. The Lead Slowing Down Spectrometer installed at the WNR neutronsource in Los Alamos National Laboratory.

Q1

laboratory portrait


separation in mass and charge of bothfragments, fragment kinetic energy, fis-sion neutron multiplicity, and energiesfor tens of actinides and subactinides.The detectors required for the projectare currently being designed. Thisexperiment is expected to be a realbreakthrough in the experimental studyof nuclear fission and to enrich very sig-nificantly both quantitatively and quali-tatively our knowledge on the fissionmechanism and at the same time thedata bases required for applications.

In a more applied field, a program incollaboration with the CEA/IRFU inSaclay for characterizing the delayedneutron emission in gamma-induced fis-sion is carried on for a selection ofactinides. The purpose is to provide datafor libraries and evaluations in the frame-work of applications for nuclear materialdetection in freight transportation [15].

In the future, the structure of fis-sion fragments will be extensivelystudied at projected facilities such asSPIRAL2, which is scheduled toproduce its first radioactive beam in

2015 in GANIL, or at the projectedEURISOL facility. That availability offission fragment beams will eventuallyproduce strong experimental constraintsfor theoretical nuclear structure, as wellas key ingredients for fission studiesrelative to the prompt and delayeddecay of fission fragments.

Theoretical Fission Studies The theoretical counterpart to the

fission measurements described earlierconsists in attempting to understandand describe the observables associatedwith the fission process using micro-scopic theoretical physics approaches.Approaches built on the establishedmany-body treatment of nuclear struc-ture (see the earlier section “TheoreticalNuclear Many-Body Problem”) aredeveloped today. In the mean-fieldframework, the potential energy of thefissioning nucleus can be calculated as afunction of collective coordinates (likeelongation, asymmetry, etc.). This poten-tial energy surface can then be used tospecify a scission line and fission frag-

ments properties at each point of thatscission line [16]. That potential energysurface can also be further used as apotential for the dynamical solving [17]of the time-dependent Schrödinger equa-tion for the collective wave function ofthe fissioning nucleus. By calculating theflux of that wave function transmittedthrough the scission line, fission frag-ment yields can be predicted using onlythe Gogny effective interaction as input.The theoretical fission fragment yieldscalculated in this manner are qualita-tively close to experimental values.

Finally, the prompt neutron andgamma emission can be predicted byallowing the fission fragments (ofwhich the yields and characteristics arecalculated above) to decay according tothe statistical model. Again, the observ-ables calculated in this way are qualita-tively comparable to experimental data.That qualitative agreement shows thatthe leading order effects are allincluded properly in the calculations.

Besides the obvious thematic over-lap with nuclear data for applications,fission is also a formidable laboratoryto challenge our understanding of fun-damental nuclear structure. For exam-ple, fission modeling involves largeamplitude collective motion of thenucleus, dynamic coupling betweenseveral collective modes, as well asbetween collective and individual(particle-hole) degrees of freedom.The theoretical and experimental studiesof fission are thus strongly linked to themore fundamental understanding of thestatic and dynamic structure of nuclei farfrom equilibrium configurations.

Nuclear Physics in Plasmas, Nuclear Physics with Lasers, and Nuclear Isomers

The isomeric states play an impor-tant role in nuclear physics. Nuclearisomers are very good probes to study

Figure 3. Mean energy of prompt fission neutron for the 238U(n,f) reactionmeasured at LANSCE (symbols) as a function of the incident neutron energycompared with model calculations (curve).

Q1

laboratory portrait


nuclear structure, because of their usu-ally pure or quasi-pure single particleconfigurations. The experimental infor-mation collected in those studies is ofcourse compared to the predictions ofnuclear structure theoretical models,and contributes to their experimentalvalidation.

Moreover, the understanding ofthe formation and de-excitation ofnuclear isomers is a scientific chal-lenge. Our laboratory is involved invarious fields, centered on the iso-mers’ properties: nuclear momentmeasurement, interaction processesbetween isomer and neutron, and iso-mer excitation in plasmas.

Nuclear Moments of Isomeric Nuclei Measurement of electromagnetic

moments is of wide interest in sub-atomic physics. In nuclear physics,within the extremely simplified single-particle model, magnetic moments ofodd mass nuclei are directly linked tothe orbital occupied by the unpairednucleon. Measuring such momentsthus allows one to unambiguouslyprobe nuclear structure and its evolu-tion throughout the nuclear chart. Theelectric quadrupole moment is moresensitive to the collective nature of thestate, and is a good observable toquantify nuclear deformation.

Our laboratory is specialized inmeasuring both magnetic and electricquadrupole moments of isomericstates, and is part of the “g-rising” col-laboration. To perform such experi-ments, one should first produce nucleiin isomeric states of interest with suf-ficient spin alignment. To do so, sev-eral kinds of nuclear reaction are atour disposal: fragmentation reactions(GANIL, GSI, MSU), fission frag-ments (GSI, ILL), and (d,p) particletransfer reactions in direct kinematics(Orsay, Bruyères-le-Châtel) in order

to prepare reverse kinematics experi-ments at the future SPIRAL2 radioac-tive beam facility. These experimentsrely on the Time Dependent PerturbedAngular Distribution (TDPAD)method in combination with heavyion-γ correlations. This method takesadvantage of the perturbation of thealigned spin of the isomeric stateinduced using external magnetic orelectric fields.

Several magnetic and quadrupoleelectric moments have been measuredin the region of neutron rich nucleimainly located around the N = 28 andN = 4 0 (sub)-shell closures.

Neutron–Isomer Interaction Nuclear isomers are promising

candidates to store and release energyon request. However, the induced de-excitation of isomers comes up againstan antagonism: the higher the isomerhalf life the more difficult de-excitationis. The induced de-excitation of K iso-mers may be different because thehalf-life of K-isomers is not only dueto the spin difference but also to the Kdifference (K is the projection of thetotal nuclear spin on the symmetryaxis in deformed nuclei). At low exci-tation energy, K can be approximatedto be a good quantum number and thenuclear transitions depend on Kconservation. At neutron separationenergy, a complete disappearance of Kquantum number is expected. Hinderedtransition between two states with alarge K difference could thus be cir-cumvented via the formation of acompound nucleus.

The 160-day 23/2− isomer in 177Lulocated at 970 keV is a candidate forobserving an induced de-excitation byneutron scattering. During a collisionbetween a neutron and an isomer, thenucleus can partly transfer its excita-tion energy to the scattered neutron

leading to the de-excitation of the iso-mer. This process is called neutronsuper-elastic scattering.

To address this process study, col-laboration between CEA laboratoriesproduced a 177 mLu target at the InstitutLaüe Langevin in Grenoble by ther-mal neutron irradiation of a highlyenriched (99.993%) 176Lu powder.Following the irradiation period, thesample was cooled down to removethe 177Lu ground state, which is shortlived (6.647 ± 0.004 days) comparedto the isomeric state (160.44 ± 0.06days). Finally, nanograms of Lute-tium, 1014 atoms, were extracted bychemical separation before producingthe isomeric targets by a direct depositmethod on backings.

To measure the super-elastic cross-section at neutron thermal energy, weused an original method involving twotypes of measurements: the isomerradiative capture cross-section and theisomer burn-up cross section. Thesuper-elastic cross-section, 258 ± 58 b,was obtained by subtracting the radia-tive capture cross-section from theburn-up cross-section. This is thehighest value ever measured for thisprocess. The ratio between the super-elastic and radiative cross-sections isclose to 0.6, showing the importanceof the neutron-induced de-excitationchannel. This encouraged us to pursueinvestigations by directly measuringthe super-elastic process. That pro-gram is in progress at the Orphée reac-tor in Saclay.

Nuclear Excitation in Plasma The last decade witnessed a fast

development of power lasers that nowallow studying matter in extreme den-sity and temperature conditions. Withthese lasers, it has become possible tocreate plasmas at high enough tem-peratures to induce high fluxes of

laboratory portrait


energetic particles in a highly ionizedmedium.

Under these conditions, the atomicnucleus is not left unperturbed. On theone hand, the plasma particles caninduce nuclear reactions, and on theother hand, the modification in theelectronic environment of the atomgreatly modifies interaction processesbetween the nucleus and the atom, suchas nuclear lifetime and reaction rates.

For heavy nuclei, the nuclear life-time of discrete levels is often stronglydependent on internal conversion,which involves bound electrons. Inplasma, many of these electrons are nolonger in a bound state and the internalconversion rate can be significantlyreduced. Its coupling with its inverseprocess (Bound Internal Conversion),Nuclear Excitation by Electronic Cap-ture (NEEC), can lead to greatlyincreased nuclear lifetimes.

In some cases, an atomic transitioncan be coupled with a nuclear transitionin a process called Nuclear Excitationby Electronic Transition (NEET) if

their transition energies are closelymatched. This can accelerate the de-excitation of the excited nuclear level,and reduced its lifetime.

We developed a model able to dealwith these processes in plasma underthermodynamic equilibrium. It evalu-ates internal conversion, NEEC, andNEET rates in plasma. Depending onthe particular situation, we used anaverage atom description or a MultiConfiguration Dirack Fock (MCDF)approach to describe the electronicenvironment of the atom. Large varia-tions of several excited nuclear-levellifetimes have been predicted. Forexample, the first excited state of201Hg, an excited level lying1.565 keV above ground state, has ade-excitation lifetime that increasesfrom 81 ns under laboratory condi-tions up to 1 ms when the plasma tem-peratures reaches around 1 keV(Figure 5). A complete description ofthe nuclear lifetime must also includesome other nuclear levels throughwhich indirect nuclear excitation or

de-excitation may occur with signifi-cantly different lifetimes.

Nuclear Data The fundamental knowledge of

nuclear physics is not directly usablefor applications such as energy produc-tion using thermal or fast spectrum fis-sion reactor (GEN IV project), fusionstudies (ITER), shielding, medical,geological, and space applications. Forthat purpose, the available experimen-tal and theoretical information must besynthesized into the so-called evaluatednuclear data files. Across the world,several approaches of that synthesisprocess (called evaluation) are put intopractice. SPN has chosen to focus onan approach that uses the results ofnuclear reaction models, whose param-eters are constrained by experimentaldata. This approach implies dedicatedwork on nuclear reaction models on theone hand, and nuclear reaction experi-mental data on the other hand.

Nuclear Reaction Modeling Because nuclear reaction models

are at the heart of our nuclear data eval-uation process, they constitute animportant focus of our laboratory. In thecontinuum region (above the resonanceregion), the relevant nuclear modelsare the optical model for direct reac-tions, pre-equilibrium models, and thestatistical Hauser-Feshbach decay ofthe compound nucleus.

Depending on the availability ofenough experimental data to constrainthe model parameters, two options areopen for the modeling of nucleon-induced direct reactions. When exper-imental constraints are available, thedispersive phenomenological opticalmodel potential [18] allows very pre-cise restitution of experimental scat-tering measurements. Conversely, if

Figure 4. Potential energy surface of the 238U fissioning nucleus calculated as afunction of the quadrupole and octupole collective coordinates, within the HFBframework using the D1S effective interaction.

Q1

laboratory portrait


experimental data is unavailable,direct reactions observables can bepredicted with the semi-microscopicoptical model potential [19], builtusing nuclear radial densities obtainedfrom HFB theoretical nuclear struc-ture calculations. In between thesetwo lies the global phenomenologicaloptical model potential [20], which iswidely used due to its ease of use aswell as its globally good quality. Fordeuteron-induced direct reactions, theCDCC (Continuum Discretized Cou-pled Channels) approach [21] hasbeen developed to explicitly take intoaccount the break-up of the weaklybound deuteron.

An essential ingredient of themodeling of the statistical compoundnucleus decay is the level density ofeach possible final state of the com-pound nucleus. To go beyond theadjusted level density formulae basedon the Fermi gas model, a combinato-rial approach [22] that uses single-par-ticle levels from HFB structurecalculations has been developed.

The aforementioned ingredientsare combined in the TALYS [23]nuclear reaction code, which is devel-oped in collaboration with NRG Petten(Netherlands). TALYS includes manystate-of-the-art nuclear reaction modelsto cover all the main reaction mecha-nisms encountered in light particle-induced reactions up to 200 A MeV. Itcan provide a complete description ofall the open reaction channels with onlya minimal input (4 lines), but can alsobe operated in expert mode using many(over 250) keywords that specifyoptions and parameters for the nuclearmodel calculations.

The modeling of high-energy reac-tions is also of interest for applicationslike Accelerator Driven Systems,shielding, or assessment of effect ofhigh-energy particle on electronics in

aerospace applications. Such calcula-tions can be performed using theBRIC-BRIEFF [24] intra-nuclear cas-cade code. That code has recently beenextended toward incident nucleon ener-gies as low as 14 MeV, which overlapwith the energy region where theTALYS code is relevant, allowing forinter-comparisons between codes.

Experimental Nuclear Data Measurements

Experimental nuclear data isessential to constrain as well as vali-date the nuclear reaction modelsdescribed earlier. Besides the fissionexperimental works, which are alreadycovered in the section on experimentalfission studies, the (n,xn) reaction is theprominent non-elastic process for fastneutrons incident on non-fissionablenuclei. For example, in the 7–20 MeVenergy range the (n,2n) reaction is oneof the most important nuclear-reactionchannels. Simulation codes involveseveral models (optical model, directinteraction, pre-equilibrium, and evapo-ration) to reproduce the whole reactionprocess. Among these processes, thepre-equilibrium is clearly the leastwell known. Although some of theexisting models are able to reproduceintegrated observables, differentialmeasurements are more challenging.

In order to provide experimentalinformation relevant to the pre-equilibrium process, we have per-formed an original measurement ofthe energy spectra of neutrons in(n,xn) reactions in coincidence withneutron multiplicity. Contrary to“classical” (n,xn) reaction measure-ments where all the channels emit-ting at least one neutron are takeninto account, the double differentialcross-section in (n,2n) tagged reac-tions are extracted. The CARMEN

detector was specially designed forsuch studies and was used in coinci-dence with NE213 neutron detectors.These measurements were performedbetween 8.3 and 13.3 MeV on Bi andTa targets [2].

The neutron–deuteron interactionis also under experimental investiga-tion in parallel to theoretical studies.A rigorous calculation of the neutron-induced deuteron break-up cross-sectionwas carried out for neutron energiesup to 30 MeV. The quality and consis-tency of the existing experimental andevaluated data lead us to believe thatthe evaluated cross-section of theneutron-induced deuteron break-upexhibits uncertainties of the order of20–30%. New and more accurateexperimental data are thus necessary tocover the 5–10 MeV and 15–30 MeVenergy ranges.

Such measurements were per-formed on the low background andcollimated beam-line of the Tandem7 MV accelerator (now decommis-sioned) in Bruyères-le-Châtel. A scin-tillation detector C6D6 is used asdeuteron target and is set up within thereaction chamber of the CARMENdetector that allows one to count thenumber of outgoing neutrons emitted

Figure 5. Nuclear lifetime of theisomeric level of 201Hg.

laboratory portrait


in a D(n,2n) reaction. A NE213 detec-tor is placed in the beam to monitorthe neutron flux, and ensures the nor-malization of the measured D(n,2n)cross-section.

Evaluation Activities The last step in the evaluation pro-

cess consists in using nuclear reac-tions codes to produce evaluated datafiles that are consistent with the avail-able experimental information, thussynthesizing the theoretical and exper-imental knowledge of the day. Forpresent day nuclear energy applica-tions, the most important reactions areof course the neutron-induced reac-tions on the major actinides 235,238Uand 239Pu. These involve adjustingthe many parameters associated withthe phenomenological modeling of thefission process [25] using constraintscoming from both nuclear physicsexperiments and critical assemblyintegral experiments. We collaboratewith CEA DEN Cadarache on both thevalidation of nuclear data files andtheir extension toward the resonanceregion. Once a nuclear data file iscomplete and validated it is submittedto the JEFF (Join European FusionFission) project, to be further testedand eventually included in the JEFFnuclear data library (NDL). The JEFFNDL is a reference library of evaluatedand validated nuclear data, recom-mended for use in fusion and fissionapplications. In the most recent JEFF3.1 neutronic library released in 2006,out of 381 isotopes, SPN has contrib-uted to 8 (n+ 103Rh, 127,129I, 236,237,238Uand 239,240Pu). For the coming JEFF 3.2library, more isotopes are prepared incollaboration with CEA DEN Cadaracheand NRG Petten.

In parallel, a significant effort hasbeen devoted to the new JEFF3.1.1

Decay Data and Fission Yieldssub-library.

The next frontier in the field ofevaluated data consists not only inproviding the best possible nucleardata based on the synthesis of theavailable experimental and theoreti-cal knowledge, but also in estimatingthe uncertainties associated withthese evaluated data. These uncer-tainties are used to assess the operat-ing margins of future nuclear energyprojects like the GEN IV nuclearreactors. The rigorous estimation[26] of these uncertainties needs totake into account both the dispersionand error bars of experimental data,as well as the uncertainties associatedwith the models and their parameters.A large international effort is under-way to produce uncertainty informa-tion for the new files in the futureJEFF 3.2 release.

Conclusions The Service de Physique Nucléaire

of the CEA DAM Ile-de-Francecontributes equally to the advance-ment of knowledge in fundamentaland applied nuclear physics. SPN isdeeply involved in many collabora-tions, both present and future, withinCEA, in France, in Europe, andinternationally. The theoretical andexperimental studies performed inSPN contribute to the excellence ofFrench institutional research atlarge, and to the scientific credibilityof the CEA DAM programs in par-ticular.

References 1. http://www.efnudat.eu2. I. Lantuéjoul, PhD Thesis, University

of Caen (2004). 3. A.A. Bergman and al. Proceedings of

the First International Conference on

Peaceful Uses of Atomic Energy,Geneva, vol 4, 1995, p 135.

4. J.F. Berger, M. Girod, D. Gogny,Comput. Phys. Comm. 63, 365 (1991).

5. J. Dechargé, D. Gogny, Phys. Rev. C21, 1568 (1980).

6. S. Peru, H. Goutte, Phys. Rev. C 77,044313 (2008).

7. N. Pillet, J.F. Berger, E. Caurier, Phys.Rev. C 78, 024305 (2008).

8. E. Clement et al., Phys. Rev. C 75,054313 (2007).

9. J.P. Delaroche et al, Nucl. Phys. A 771,103 (2006).

10. G.F. Bertsch et al. Phys. Rev. Lett. 99,032502 (2007).

11. F. Chappert, M. Girod, S. Hilaire,Phys. Lett. B 668 420 (2008).

12. Fréhaut et al., EXFOR reference W,Frehaut, 8009.

13. J.F. Berger et al., Nucl. Phys. A42823c (1984).

14. T. Ethvignot et al., Phys. Lett.B575,221 (2003); T. Ethvignot et al.,PRL 94, 052701 (2005); J. Taieb et al.,Proceedings of the Nuclear Data Con-ference, Nice 2007.

15. D. Doré et al., Proceedings of theNuclear Data Conference, Nice 2007.

16. N. Dubray, H; Goutte, J.P. Delaroche,Phys. Rev. C 77, 014310 (2008).

17. H. Goutte et al., Phys. Rev. C 71,024316 (2008).

18. B. Morillon, P. Romain, Phys. Rev. C70, 014601 (2004).

19. E. Bauge, J. P. Delaroche, M. Girod,Phys Rev. C 63, 024607 (2001).

20. A.J. Koning, J. P. Delaroche, Nucl.Phys. A 713, 231 (2003).

21. Huu-Tai P. Chau, Nucl. Phys A 773,56 (2006).

22. S. Hilaire, S. Goriely, Nucl. Phys. A779, 63 (2006).

23. http://www.talys.eu 24. H. Duarte, Phys. Rev. C75, 024611

(2007). 25. M.J. Lopez-Jimenez, B. Morillon, P.

Romain, Ann. Nucl. Energy 32, 195(2005).

26. M.B. Chadwick et al., Nucl. DataSheets 108, 2742 (2007).

ERIC BAUGE

Bruyères-le-Châtel

feature article


Deep Underground Laboratories—Somewhere Quiet in the Universe

NEIL SPOONER University of Sheffield, ILIAS, LAGUNA, and Boulby Laboratory

Introduction: Nobel and Noble Dreams The world’s very deep underground laboratories offer

access to the ultimate in quiet environments for scienceresearch. Here the term quiet generally refers to the cosmic-ray muon flux that is greatly reduced in these laboratoriescompared to that at the surface. It is this feature that allowsobservation or searches for very rare fundamental physicsprocesses, impossible to undertake on the surface becauseof the muon-induced background. Perhaps most notable ofthese is solar neutrino physics, for which, after a long his-tory, Ray Davies received in 2002 with Masatoshi Koshibathe Nobel prize for measurement of neutrinos from the Sun.Such work falls firmly within the field of ParticleAstrophysics—the use of particle physics to study astro-physics and of astrophysics to study particles. However, inthe underground world quiet increasingly means also lowvibration noise, low electrical noise, low natural radiation,low radon gas, and even low biological contamination.Realization of this, and that for particle physics the next bigenergy frontiers may in fact more economically be reachedvia new opportunities underground than at accelerators, isstarting to generate a revolution of development. Large newexperiments are planned, many laboratories are pushingexpansion schemes, and new deep laboratories are beingbuilt. The discipline once termed Underground ParticleAstrophysics and devoted mainly to solar neutrinos is trans-forming into a diverse field, itself becoming a sub-topic ofa new interdisciplinary field called simply UndergroundScience.

This renaissance is perhaps best exemplified by theenthusiasm for construction in the United States of a hugelyambitious new national laboratory, the Deep UndergroundScience and Engineering Laboratory (DUSEL) [1]. Afteran intense competition over several years the location of the£0.5B DUSEL was chosen in April 2007 to be the disusedHomestake Gold Mine in South Dakota. The laboratory hasalready attracted interest as a site for around 100 experi-ments, split between particle astrophysics and a range of newscience that includes significant microbiology interests.

Notable among the latter is work on so-called Dark Life,the search to understand the origins of the microbial lifefound in abundance in deep rock. Around 50% of theworld’s total biomass is underground. Dark Life aside,DUSEL, if given the final go-ahead by the U.S. Congress,is hugely exciting for nuclear and particle astrophysics,providing opportunities for the United States to contributebetter to the growing range of large, next generation experi-ments being developed at European sites and in Asia.Among these is a growing enthusiasm for the use of liquidnoble gas technology, argon, neon, and xenon, as possiblythe next great detector technology (see Figure 1).

The World’s Deep Laboratories—Deep and Dirty To put this in context, shown in Table 1 is a compen-

dium comparing vital characteristics of the world’s currentand up-coming most well-known deep underground sitesand in Table 2 an overview of the experimental activity andstatus of expansion plans, where known (see also Ref. [2]and related sources). The first characteristic generally ofinterest to users is the depth (Table 1, column 4) becausethis is related to the level of cosmic-ray shielding providedby the rock. Traditionally, this is given in m.w.e. (meterswater equivalent), the depth normalized to the density ofwater (to allow for different rock types). However, greatcaution is needed with m.w.e. because this may refer just tothe vertical depth above the laboratory which, for a minesite in particular, tends to underestimate the relative shield-ing, because most lines of sight from the laboratory to thesurface pass through a greater thickness of rock than that ofthe vertical depth. A better comparison for most purposes,which naturally accounts for the averaging of the rockcover, is to use the actual measured muon flux (also in col-umn 4). This also accounts for the slight effect of differentlatitudes and altitudes. It should be noted here that there area much larger number of underground laboratories at shal-lower depth not shown here, for instance as covered inEurope by the organization CELLAR [3]. These sites, ingeneral less than 200-m deep, undertake, for instance, low

Q1

feature article


background measurements of materials but are not involvedin front-line fundamental research.

Perhaps unique to the deep laboratories (see Table 1), isthe significant range of characteristics that reflect not just therequirements of the science but the severe constraintsimposed by geographic and local economic factors requiredfor establishing a deep underground site. This arises becauseunderground science alone has not so far provided sufficientjustification to fund the necessary access excavation. Rather,almost all sites piggyback off an existing underground infra-structure, usually a public road tunnel or deep mine. This sit-uation introduces other peculiarities and challenges for the

laboratories. In particular, the need to cooperate closely withthe host owners, the public road authorities, mine company,national park, or other bodies that all impose constraints.

These economic and ownership factors have partly lim-ited both the number of sites and their scope for expansion,resulting in a significant lack of deep space for science, par-ticular at greater depths. Recognizing this, there has been atrend in recent years toward better coordination betweenlaboratories, to exchange best practice and experience toimprove efficiency for the user, but also toward coordi-nated, more efficient, allocation of space. The aim being tosite experiments at the laboratories best suited to their sci-entific needs rather than for geographical reasons. A partic-ular case is dark matter experiments searching for WeaklyInteracting Massive Particles. As the need to probe to ever-lower cross-sections increases, so does the need for greaterdepth, to reduce further the muon-induced neutron back-ground. Some priority will be needed to move next genera-tion dark matter experiments to sites with the necessarydepth, while other classes of experiment proposed, forinstance for proton decay using liquid argon like GLA-CIER, can function comfortably at shallower sites [5].

Coordination between laboratories is exemplified inEurope by the highly successful new organization ILIAS(Integrated Large Infrastructures for Astroparticle Science)[6]. Set up in 2003 and funded by the European Union,ILIAS has brought together the four main deep laboratoriesin Europe—Boulby, Canfranc, Frejus, and Gran Sasso.ILIAS involves over 20 institutes representing around 1,500scientists with interest in underground physics and gravita-tional waves. ILIAS is run through a set of six networks,three joint research projects, and a Trans-national AccessProgramme (TA). Particular success has been production ofthe first databases collecting together information on lowbackground materials and techniques produced by the labo-ratories [6]. A specific laboratory network has produced jointsafety training and policy activity and, through regular meet-ings between the directors, progress toward coordinating sci-ence policy. The TA underpins much of ILIAS, providing ajointly run fund to which groups can apply for resources togain access to any of the laboratories.

Important Comparative Features—Rock and a Hard Place

Comparing again the characteristics of the laboratories(Table 1), several particular features and their interactionwith the science are worth noting.

Figure 1. The first ton-scale dark matter detector, ArDM,uses liquid argon—seen here undergoing tests at CERN [2].

feature article


Table 1. Summary characteristics of the world’s deep underground laboratories.

Site Location and access Current space Depth and muon flux (m m-2 s-1)

Rock and radon (Bq m-3) Neutrons (m-2 s-1)

Europe

BNO Andyrchi, Russia; independent tunnel

3 halls: 24 × 24 × 16 m3;60 × 10 × 12 m3;40,000 m3

850 m.w.e. and 4,700 m.w.e. (SAGE area); 3.03 ± 0.19 × 10−5

40 norite rock 1.4 × 10−3 (>1 MeV); 6.28 × 10−4 (>3 MeV)

BUL Boulby mine, UK; vertical

1,500 m2 2,800 m.w.e. under flat surface; 4.5 ± 0.1 × 10−4

1–5 salt 1.7 × 10−2 (>0.5 MeV)

CUPP Pyhasalmi mine, Finland; vertical

>1000 m2 spaces no longer used by the mine

down to 1,400 m — pyrite ore, zinc ore

—

LNGS Gran Sasso, Italy; road tunnel

3 halls plus tunnels total 17,300 m2; 180,000 m3

3,200 m.w.e., under mountain; 3 × 10−4

50–120 CaCO3 and MgCO3

3.78 × 10−2 (total); 0.32 × 10−2 (>2.5 MeV)

LSC Canfranc, Spain;road tunnel

2 halls: 40 × 15 × 12 m3; 15 × 10 × 8 m3;tot 1,000 m2

2,400 m.w.e., under mountain;2 × 10−3–4 × 10−3

50–80 limestone, 2 × 10−2

LSM Modane, France; road tunnel

1 hall and service areas: 400 m2

4,800 m.w.e. under mountain; 4.7 × 10−5

15; (0.01 filtered) calcitic schists

5.6 × 10−2 (work in progress)

SLANIC Prahova mine, Romania; vertical

70,000 m2 average ht. 52–57 m

208 m, under flat surface 6 salt —

SUNLAB Sieroszowice mine, Poland; vertical

85 × 15 × 20 m3 900–950 m (2200 m.w.e.) 650–700 m for large caverns

20 salt and copper ore

—

SUL (Uk) Solotwina mine, Ukraine; vertical

25 × 18 × 8 m3; 4 of 6 × 6 × 3 m3; total area 1,000 m2

1,000 m.w.e. under flat surface; 1.7 × 10−2

33 salt <2.7 × 10−2

Asia

INO (proposed) Masinagudi, India; independent tunnel

2 halls: 26 × 135 × 25 m3;53 × 12 × 9 m3

3500 m.w.e. — compactedgranite

—

Kamioka Japan; independent horizontal

Hall SK 50 m dia; 40 × 4 and 100 × 4 m wuth L-arm

2700 m.w.e. 3 × 10−3 20–60 lead andzinc ore

8.25 ± 0.58 × 10−2 (th); 11.5 ± 1.2 × 10−2 (fast)

Oto-cosmo Tentsuji, Japan;Indep. horizontal

2 halls: 50 m2; 33 m2; total ~100 m2

1400 m.w.e. 4 × 10−3 10 (radon reduced)—

4 × 10−2

Y2L YangYang, S. Korea; horizontal

Current space: 100 m2 Planned space: 800 m2

~2000 m.w.e. 2.7 × 10−3 40–150— 8 × 10−3 (1.5–6.0 MeV)

North America

DUSEL (proposed)

Homestake, USA; vertical

7,200, 4,500, 100 m2 at 1,450, 2,200, 2,438 m dep

233, 4,100, 6,400, 7,000m.w.e. under flat surface

~40–200 (at 1478 m)metasedimentary

—

SNOLAB Creighton mine, Canada; vertical

SNO ~200 m2; main 18 × 15 × 15–19.5 m3; ladders 6–7 m;total 46,648 m3

6,001 m.w.e. under flat surface 3 × 10−6

120; norite, granite gabbro

4.7 × 10−2 (th) 4.6 × 10−2 (fast)

SUL (US) Soudan mine, USA;~ vertical

2 halls: 72 × 14 × 14 m; 82 × 16 × 14 m; tot 2,300 m2

2,000 m.w.e under flat surface 2 × 10−3

300–700; Ely greenstone

2 × 10−2 (calc)

WIPP Carlsbad, USA; vertical

500 × 8 × 6 m available 2,000 m.w.e. 2 × 10−3 expected

<7; salt 115+/−22 m−2d−1 (th + ath)

Kimballton Butt Mountain, USA; horizontal

30 × 11 × 6 m 1,400 m.w.e — Paleozoic dolomite

—

feature article


Table 2. Deep undeground experiments and plans.

Site Users (approx.) Current experiments Future plans

Europe

BNO Staff 50–60; Users 30–35

Neutrinos: BUST; SAGE Uncertain

BUL Staff 2; Users 30

Dark Matter: ZEPLIN II, ZEPLIN III, DRIFT II; Other: SKY, ongoing R&D, HPGe measurements, geophysics

Expansion to deeper hard rockunderway; LAGUNA

CUPP Staff 3–6; Users 10

Muons: EMMA Expansion study; LAGUNA

LNGS Staff: 64 + 23 Users: 750

Dark matter: LIBRA, CRESST2, XENON10, WARP; Double Beta Decay: COBRA, CUORICINO, GERDA; Solar/geo/SN/beam neutrinos: BOREXINO, LVD, OPERA, ICARUS; Nuclear astrophysics: LUNA2; Other: VIP, LISA, R&D, HPGe, geology, biology, environmental studies

MODULAr—New facility at shallow depth (1,200 m.w.e.) proposed

LSC Being defined Being defined by open call. In old lab: ANAIS, Rosebud, R&D activity, 4 HPGe detectors

LAGUNA

LSM Staff 8–9; Users 100

Dark Matter: EDELWEISS; Double beta Decay: NEMO, BiPo, TGV; Other: SHIN, HPGe detectors

ULISSE: 2 new halls: 100 × 24 m; 18 × 50 m (with water shield). MEMPHIS, LAGUNA

SUL (Uk) Staff 14; Users 11+

Double Beta Decay: 116CdWO4 scintillators, SuperNEMO R&D; R&D on: CaWO4, ZnWO4, PbWO4, CaMoO4, new molybdates

Uncertain

SLANIC Variable MicroBq laboratory and whole body counting HPGe spectrometry; nuclear astrophysics; LAGUNA

SUNLAB Being defined Being defined LAGUNA

Asia

INO (proposed) Staff: 50–100 ICAL—50 kt magnetized Fe tracking calorimeter for atmospheric and very long base-line accelerator neutrinos

Plans being prepared

Kamioka Staff: 13 + 2 Users: >200

Neutrino astrohysics and beam: Super-Kamiokande, XMASS prototype, KAMLAND; Dark Matter: NEWAGE, XMASS; Gravity: CLIO; Double Beta Decay (proposed): CANDLE.

New halls: 15 × 21 m for XMASS 800 kg; 6 × 11 m for CANDLE; gravitational antenna LCGT request; Hyper-K study

Oto-cosmo Users: ~20 Double Beta Decay, Dark Matter: ELEGANTV, MOON-1, CaF2

uncertain

Y2L Users: ~30 Dark Matter: KIMS; Double Beta Decay R&D; HPGe Can be expanded as desired

North America

DUSEL(proposed)

Staff: >80Users: >200

First experiments through SUSEL Inc. LUX (Dark Matter)

Expansion depends on approval

SNOLAB Staff: ~30 Users: >100

Neutrino astrophysics/Double Beta Decay: SNO+; Dark Matter: DEAP/CLEAN, PICASSO; Letters being considered

SuperCDMS, EXO. Further site expansion limitedby rock removal

SUL (US) Staff: 9 Users: >200

Neutrino beam: MINOS; Dark Matter: CDMS II; low background

Uncertain

WIPP Staff: as needed Double Beta Decay R&D: EXO, MEGA/SEGA, MAJORANA

Expansion to fill designated area

Kimballton Staff: as needed Neutrino astrophysics: LENS, R&D Expansion to fill designated area

feature article


The Rock The geology of a site is of course a critical factor. First,

it determines the natural radiation background, bothgamma, principally from the U, Th, and K levels in therock, and the neutron background, from rock fission andmuons [7]. These backgrounds are critical for most particleastrophysics experiments and require expensive passive oractive shielding techniques, the design of which, princi-pally the thickness and hence the cost, depend on this back-ground. Extreme examples of note are sites in salt, such asWIPP, Boulby, and Slanic, for which the natural rock back-ground can be exceptionally low. In harder granite-typerock, the background can be higher by 100 times or more.Although the background gamma flux is straightforward tomeasure, using a Ge detector for instance, it is much morechallenging to determine the ambient fission and muonneutron background. New measurement techniques arebeing developed for this, for instance at Boulby andModane [7,8]. Interestingly, these confirm simulationsshowing that although salt provides a gamma backgroundsignificantly improved over other rock forms, the scatteringprocess for neutrons in salt means the neutron backgroundis not improved by nearly the same factor.

The uranium content of the rock, together with the geol-ogy, porosity, and the ventilation characteristics, also criti-cally determine the radon levels. Contamination by radonand its daughters is a major issue for many experimentswith widely different concentrations encountered in the dif-ferent sites. Again salt wins here with levels typically of afew Bqm−3, compared to 100–1,000 times more in someother sites (see Table 1). Nevertheless, all sites need to takeprecautions. At Modane for instance, a dedicated radonreduction plant has been pioneered that uses an array ofcooled carbon filters [8]. Such plants will need to feature innew excavations seeking the lowest backgrounds.

The rock type, in combination with the depth, seismicactivity, faulting, water ingress, and other geology, obviouslyalso determines the form of cavern that can be constructed,most notably the maximum safe height. Salt, for instance,undergoes plastic flow at depth, which restricts the excava-tions (without significant extra support) to heights perhaps<15 m, as at Boulby. Here, though, the length of excavationis essentially unlimited. However, at shallower depths, suchas Slanic, this restriction relaxes. Here extraordinary cavernsof 40–50 m in height have been in use for many decades(Figure 2). To create larger caverns at depth, harder rock,such as at Gran Sasso, is essential, although again depth is anissue as the rock pressure increases. The SNO cavity at

Creighton mine currently holds the record for the largest sin-gle cavity at depth.

Tunnel versus Mine One striking difference between the sites for the user is

the division between tunnel-based and mine-based sites.The advantages held by the former are often cited, forinstance the benefits of horizontal access, such as atModane and Gran Sasso. Meanwhile, a key disadvantage ofa mine site is often stated to be the dependency on the mineowners, particularly the implications of cessation of min-ing. However, while horizontal access may be an advantageduring experiment construction, allowing large single loadsto be delivered by lorry, for the individual user vertical,walk-in, lift access, direct from a nearby surface facility,can be more convenient. Meanwhile, mine companies, suchas INCO at SNOLAB or CPL at Boulby, are anyway wellused to transport large items down shafts and fabricatingunderground—a process that can also allow better controlof cleanliness for an experiment.

Although it is clear that good relations are needed withmine owners for those sites, it is also the case that road tun-nel sites are at the mercy of the relevant tunnel authorities.One concern is safety. This is a key matter in both cases butparticularly for tunnel authorities because of the presencenearby of the general public, an increasing issue for tunnelshighlighted in the Alpine sites by several recent fires. Theadvantage at a mine is that access for all personal is strictlycontrolled, there is no presence of mass general publicnearby to consider, specific safety and evacuation training

Figure 2. The Slanic site in Romania—a relatively shallowsite but with exceptionally large caverns excavated in salt.

feature article


can be made compulsory for all, changed and improved asneeded and the location of everyone can be monitored andcontrolled. Any incident can therefore be contained morequickly and is likely to have fewer repercussions.

This degree of available control makes mine sites possi-bly also more suitable for future experiments requiringunusual or potentially dangerous materials, such as, forinstance, large volumes of cryogenic gases or low flash-point scintillators. The flexibility of mine sites throughdirect access on-site to excavation machinery and miningengineers, is a further advantage here. It allows existingcaverns to be adapted or new ones built quickly if neces-sary, whereas for tunnels, once the road or dam buildinghas been completed, major changes are problematic exceptin special circumstance. This ready prospect for new exca-vation also opens advantages for interdisciplinary science,notably access to fresh, uncontaminated rock. This is keyfor potential microbiology applications and in geophysicsand engineering projects, such as waste management stud-ies. Finally, no existing tunnel site can provide access to thegreat depth needed by many upcoming physics experi-ments, at least not without excavating a vertical shaft!

Geographic Location A final point worth highlighting here are issues arising

from geographic location. Through the dependency on adeep mine or mountain range to provide the over-burden,all current deep laboratories are located in relativelyremote, rural areas. This introduces extra challenges for theuser, notably from the limited transportation options,lengthy travel times, the limited nearby accommodation,

and the potential lack of a collegiate social atmosphereaway from home institutions. These are challenges for thelaboratory directors but arguably worse in some cases arethe environmental challenges, particularly in Europe now,where all four deep sites are in national parks. This has, forinstance, restricted surface laboratory development atBoulby and at Gran Sasso has halted expansion plans inpart due to the environmental impact on the local watertable. All site developments increasingly need to takeaccount of environmental impacts.

More importantly, site location is vital to certain scienceactivity, notably neutrino physics. Here, if the best neutrinooscillation physics is to be extracted then the distance to apotential next-generation neutrino beam or factory needs tobe optimized, depending on the beam energy. Long base-lines favor better separation of matter effects from CPviolation and provide a richer neutrino physics, includingdetermining the MNSP matrix elements, especially θ13 [9].This factor has, for instance, been an issue for Soudan, beingrather too close to Fermilab (724 km) and conversely pro-vided encouragement for the development of Phyasalmi,where the distance to CERN (2,300 km) makes this attrac-tive. Conversely, the proximity of Frejus to CERN (130km)may disfavor this site. This matter was a consideration forDUSEL where the chosen site of Homestake is at 1,290kmfrom Fermilab and 2,540km from BNL. The relative remote-ness of a site like Phyasalmi or SNOLAB, away from com-mercial nuclear energy reactors is also a consideration. Theanti-neutrino background from these is, for instance, a limit-ing factor for new experiments seeking to observe the back-ground neutrino flux from past supernova, while in the newfield of geo-neutrinos location in relation to the local thick-ness of the Earth’s crust is an issue [10].

Science and Expansion—Hooray for Proton Decay There has been outstanding success recently in under-

ground physics, most obviously in solving the solar neutrinoproblem, with SNO at SNOLAB, at SuperK and Gran Sasso,but also with neutrino beam experiments, and in dark matterand double beta decay, where it has proved possible to buildever larger and more sophisticated experiments underground.Table 2 lists most of the current activity. The recent successof Borexino at Gran Sasso (see Figure 3) is a particular mile-stone, not just for successfully observing 7Be solar neutrinosin real time but because this experiment has demonstrated thefeasibility of achieving backgrounds in a large (87.9 ton,fiducial) active medium, liquid scintillator in this case, at the

Figure 3. Inside the Borexino detector at Gran Sasso.

feature article


exceptional level of 7× 10−18 g/g 323Th—a value oncethought impossible [11]. This progress, together with rapiddevelopment of new technologies, such as very large liquidnoble gas detectors, notably liquid argon, plus better under-standing of how to build large caverns at depth, points theway to a far more ambitious future.

The pinnacle here would be construction of a 100–1,000 Kton experiment (~20 times SuperK) that would pushproton decay sensitivity by one to two orders, including inthe kaon channels [5]. However, such a detector could alsomeasure the relic neutrino flux from past supernovae for thefirst time; observe neutrino bursts from new supernovae;geo-neutrinos and, with a suitable beam, unravel lepton CPviolation and measure θ13 to exceptional precision. InEurope the LAGUNA collaboration, now partly funded bythe European Commission, will study three potential tech-nologies—water cherenkov, liquid argon, and liquid scintil-lator—and investigate options for an underground site. Sixare being considered—Boulby (UK), Canfranc (Spain),Frejus (France), Phyasalmi (Finland), Slanic (Romania),and Sunlab (Poland) (see Table 2). Work has started withengineers and companies to determine the safe size andform of caverns that could be built at each site.

LAGUNA is Europe’s answer to similar megaton activ-ity in Asia and North American. DUSEL at Homestakewould now be the location for a U.S. version. In Japan,plans for HyperK are well advanced with detailed rockstudies in the region of Kamioka mine already completed[12]. However, in this region there is potential interest in alarge detector further downstream from the Tokai neutrinobeam as part of extensions to the current T2K experiments.Such a detector could be lined up with SuperK and locatedin South Korea or, as recently proposed, on the Japaneseisland of Okinoshima [13].

Although likely costing a fraction of CERN’s LHC, thescale of a nucleon decay facility means probably only onesite will ever see such an experiment. However, thevibrancy in underground science in general is seeinggrowth now anyway, with new sites emerging, such as therecently funded Indian Neutrino Observatory (INO), andmany expansions underway (see Table 2). The drive formuch of this is new dark matter and neutrino experiments,including for double beta decay. These fields are maturingand now developing a new generation of larger, multi-ton,experiments with more sophisticated background reduc-tion. In Europe, the new Canfranc halls have recently beenbuilt with this in mind and at Frejus, the deepest in Europe,ULISSE is well advanced to establish two new halls totalling

>3000 m2, made possible by the highway agency’s need toexcavate a new emergency evacuation tunnel. One of thesehalls is proposed to have an integrated water shield to pro-vide the ultimate low background room, possibly the quiet-est place in the Universe [8]!

All the LAGUNA sites in fact have general expansionplans. At Boulby for instance, the mine company is proceed-ing into new deeper hard rock areas with new science labora-tories to be made available, starting with a dedicatedgeophysics laboratory. At Phyasalmi, now the deepest minein Europe at 1400m, engineers are proposing a new facilityseparated from the main mining activity. Perhaps the best-known expansion activities are at SNOLAB and DUSEL.The Canadian site is nearing completion of an exceptionalfacility that includes the first purpose-built underground lab-oratory for experiments using cryogenic liquids, the CryopitLaboratory (see Figure 4). In the United States, althoughDUSEL, as the world’s largest currently planned new site,will need final congressional approval, the first stage is pro-ceeding anyway thanks to state donations and funds fromlocal philanthropist Mr. T. Denny Sanford (SUSEL). Thiswill see rapid restoration of the original cavern at Homestakeused by Ray Davis to make his detection of neutrinos fromthe Sun—a fitting tribute to his pioneering work in one of theoriginal Deep Underground Laboratories.

Acknowledgments The author thanks ILIAS (contract no. RII3-CT-2004-

506222) and CPL (Boulby) and LAGUNA for support.

Figure 4. Schematic plan of the new SNOLAB expansionsshowing the SNO cavern (left), new laboratories (blue), andfurther extension for the Cryopit laboratory (top right).

feature article


References 1. www.lbl.gov/nsd/homestake/ 2. L. Kaufmann et al., Nucl. Phys. B—Proc. Supp. 173 (2007), 141. 3. A. Bettini, Proc. TAUP2007, www.iop.org/EJ/volume/

1742-6596/120/8 4. M. Laubenstein et al., App. Rad. & Isotopes 61 (2004), 167. 5. J. Aysto et al., JCAP 0711 (2007), 011. 6. www-ilias.cea.fr 7. E. Tziaferi et al., Astroparticle Phys. 27 (2007), 326. 8. www-lsm.in2p3.fr/ 9. V. Barger et al., arxiv.org/abs/0705.4396 10. A. Kathrin et al., Astroparticle Phys. 27 (2007), 21. 11. C. Arpesella et al., Phys. Lett. B 658 (2008), 101. 12. N. Wakabayashi, proc. NNN07, www-rccn.icrr.u-tokyo.ac.jp/

NNN07 13. A. Rubbia et al., arXiv:0804.2111.

NEIL SPOONER

University of Sheffield andBoulby Laboratory

Q2

facilities and methods


JUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei

International collaborations filltoday’s research landscape, facilitatescientific progress, and lead to a stron-ger scientific community throughtackling mutually beneficial researchproblems. Furthermore, internationalresearch collaborations result in a cul-tural understanding among the com-munity of scientists. For these generalreasons, the Japan U.S. Theory Insti-tute for Physics with Exotic Nuclei(JUSTIPEN) was established twoyears ago. JUSTIPEN enables travelof U.S. scientists to Japan to collabo-rate with their Japanese counterpartsas the community pursues a basicunderstanding of exotic nuclei andtheir role in astrophysics and otherareas. In this brief report, I willdescribe the activities of JUSTIPENduring the last two years.

Experimental and theoretical stud-ies are now underway to attain adeeper understanding, richness, anddiversity of nuclear phenomena. Keyscientific themes that are beingaddressed are captured by five over-arching questions that have beendeveloped during the last few years.These are:

• What is the nature of the nuclearforce that binds protons and neu-trons into stable nuclei and rareisotopes?

• What is the origin of simple pat-terns in complex nuclei?

• What is the nature of neutron starsand dense nuclear matter?

• What is the origin of the elementsin the cosmos?

• What are the nuclear reactions thatdrive stars and stellar explosions?

These questions align well with thedrivers of rare isotope science. Oneprimary aspect of the first and secondquestions concerns testing the predic-tive power of models by extendingexperiments to new regions of massand proton-to-neutron ratio and identi-fying new phenomena that will chal-lenge existing many-body theory.

In order to achieve the overarchinggoal of a comprehensive descriptionof all nuclei, a new generation of rareisotope facilities is coming on-line toproduce very short-lived nuclear spe-cies in the laboratory. Notable amongthese new facilities are the Rare Iso-tope Beam Factory at RIKEN inJapan, which began operations inNovember 2006, the Facility for Anti-proton and Ion Research (FAIR) facil-ity at GSI which is under construction,and isotope separation techniques,which continue to be developed atSPIRAL-II, Ganil in France, and TRI-UMF in Canada. These new facilities,in addition to existing experimentalefforts at premier facilities such as theNational Superconducting CyclotronLaboratory at Michigan State Univer-sity and the Holifield Radioactive IonBeam Facility (HRIBF) at Oak RidgeNational Laboratory (ORNL), andincluding the proposed Facility forRare Isotope Beams (FRIB) in theUnited States, hold the key to unlock-ing the mystery of nuclei and nuclearproduction in the universe.

Theoretical investigations of nucleiand their applications will also benefitfrom experiments at current and newfacilities, and a group of Japanese andU.S. scientists realized that anenhanced theoretical collaborative

activity between the United States andJapan would benefit both countries inthis area of science. The U.S. contri-bution through the U.S. Department ofEnergy JUSTIPEN grant providestravel and local support for U.S. scien-tists to visit scientists in Japaninvolved in the study of nuclei. Mean-while, the University of Tokyo (abbre-viated as Todai in Japanese) andRIKEN have established the Todai-RIKEN Joint International Programfor Nuclear Physics (TORIJIN) inorder to enhance jointly internationalcollaborations and exchanges innuclear physics, and the University ofTokyo has created an associate profes-sor position designated for this pur-pose. One of the major purposes ofTORIJIN is obviously to host theJUSTIPEN activities including theJUSTIPEN office in the RIBF build-ing of the RIKEN Nishina Center andvarious cares for JUSTIPEN visitors.While this office is the hub of JUSTI-PEN activities, we also provide sup-port for travel to other Japanesevenues for collaborative research.Detailed information on JUSTIPENcan be found at the Web pagewww.phys.utk.edu/JUSTIPEN. Thiswebsite provides a repository of infor-mation for JUSTIPEN including visi-tor information, exit reports, detailedinformation on how to function atRIKEN, JUSTIPEN policies, andother items.

JUSTIPEN Opening, July 10–11, 2006

JUSTIPEN was opened duringmid-July, 2006. Members of the U.S.



team on this trip included SteeringCommittee members Witek Nazare-wicz (University of Tennessee), BahaBalantekin (University of Wisconsin),Richard Casten (Yale University), andDavid Dean (ORNL), as well as SidneyCoon (U.S. Department of EnergyOffice of Nuclear Physics Theory Pro-gram Manager), and Bruce Barrett (U.Arizona, and one of the initial long-termvisitors to the Institute). Also attendingthe meetings were many Japanese col-leagues; a partial list is given with theofficial picture of the opening, shown inFigure 1. During July 10, talks weregiven to explore what kinds of scientificcollaborations could come from theInstitute. Numerous ideas were put for-ward for the JUSTIPEN efforts. Policywas also discussed at the meeting.

During its first year of opera-tions, JUSTIPEN provided fundingto 10 U.S. visitors and to approxi-mately 25 visitors during its secondyear.

JUSTIPEN-U.S. During this time, Japanese col-

leagues also worked toward estab-lishing funding opportunities to sendJapanese to the United States forcollaborations. This effort broughtthem with the “InternationalResearch Network for Exotic FemtoSystems (EFES)” as a Core-to-Coreproject by the Japan Society for thePromotion of Science (JSPS). TheEFES project played major strongroles as Japanese matching fund to

JUSTIPEN, called for short asJUSTIPEN-U.S. hereafter.

The EFES initiative resulted in anexchange activity in March 2007. Thefirst Joint JUSTIPEN-LACM Meetingwas held at the Joint Institute forHeavy Ion Research (JIHIR) at ORNLfrom March 5–8, 2007. The meetingwas a merger of two workshops:(1) the annual National Nuclear Secu-rity Administration–Joint Institute forHeavy Ion Research (NNSA–JIHIR)meeting on the nuclear large ampli-tude collective motion (LACM) withan emphasis on fission, and (2) theU.S.–Japan theory meeting under theauspices of JUSTIPEN. The purposeof the meeting, jointly organized bythe JUSTIPEN Governing Board, bythe UT/ORNL nuclear theory group,and by the EFES, was to bringtogether scientists (theorists andexperimentalists) with interests inphysics of radioactive nuclei,LACM, and theoretical approachesrelated to the Scientific Discoverythrough Advanced Computting (Sci-DAC) Universal Nuclear EnergyDensity Functional (UNEDF)project (see Figure 2). The meetingconsisted of approximately 50 talkson physics of radioactive nuclei.Figure 2 includes local organizers ofthe workshop and the Japanese col-leagues. The Tandem of the Holif-ield Radioactive Ion Beam Facility(HRIBF) at ORNL stands in thebackground.

The success of the 2007 meetingled to a second meeting during 2008.The second LACM-EFES-JUSTIPENWorkshop was held during January23–25, 2008, at ORNL. The workshopprogram covered a number of topicsincluding fission/fusion and otherforms of large-amplitude collectivemotion, computational nuclear struc-ture physics, nuclear structure relevant

Figure 1. JUSTIPEN OPENING (L to R): N. Itagaki (University of Tokyo,secretary of JUSTIPEN); H. Sakai (University of Tokyo, JUSTIPEN governingboard); T. Motobayashi (RIKEN, JUSTIPEN Associate Director); W. Nazarewicz(University of Tennessee and ORNL, JUSTIPEN governing board); Y. Doi,(Executive Director of RIKEN); R. Casten (Yale University, JUSTIPENGoverning Board); B. Barrett (U. Arizona, first long-term visitor ofJUSTIPEN); D. Dean (ORNL, JUSTIPEN Associate Director); B. Balantekin(U. Wisconsin, JUSTIPEN governing board); S. Coon (U.S. DOE Office ofScience, Office of Nuclear Physics); A. Arima (President, Japan ScienceFoundation); Y. Yano (Director, Nishina Center for Accelerator Sciences,RIKEN); T. Otsuka (U. Tokyo, JUSTIPEN Managing Director); M. Ishiara(RIKEN); and Y. Okuizumi (RIKEN, head of Nishina Center Administration).



to nuclear astrophysics, gamma-rayspectroscopy, clustering in nuclei, andtopics related to ongoing and futurecollaborations with Japanese groupsand colleagues. This meeting ran con-currently with a celebration of the25th anniversary of the building of theJoint Institute for Heavy Ion Research(JIHIR) at ORNL. The JIHIR was thebrainchild of a group of physicists,including University of Tennessee pro-fessor (and former ORNL deputydirector) Lee Riedinger, UT’s CarrollBingham, and Vanderbilt University’sJoe Hamilton, to establish a means toopen the Lab’s Holifield Facility andits tools such as the Recoil Mass Spec-trometer to university users back in1982.

JUSTIPEN was the linchpin toobtain full funding for an expansion ofthe JIHIR to obtain a new “theorywing.” This expansion will enable areciprocal Japanese exchange programthat will bring our Japanese colleaguesto the United States, again to benefitresearch efforts in physics with exoticnuclei. Funding for this expansion willcome from the State of Tennessee,ORNL, the University of Tennessee,and Vanderbilt University. Construc-tion began in the spring and is nowabout 50% complete. We anticipateopening the theory wing in the winter.The extension to the JIHIR will be thehome-base for the JUSTIPEN-U.S.program and will consist of 4 single-person offices and 4 two-personoffices.

A Brief Tour of the Physics of Exotic Nuclei

Research performed throughJUSTIPEN is meant to be broad andencompasses a variety of theoreticaltechniques (see Figure 3). In this clos-ing section, I will briefly mention

some of the aspects of that research.Theoretical research of the propertiesand characteristic of nuclei necessarilyinvolves coming to an understandingof the complexity of the nuclear force,which involves two-body and three-body (at least) interactions amongprotons and neutrons, and an under-standing of how to apply quantummany-body theory to the nuclear prob-lem. Recent advances in chiral effec-tive field theory, using the pion andnucleon as the relevant degrees offreedom, have connected the nuclearforces to the underlying symmetries ofQCD, and are able to accuratelydescribe nucleon-nucleon scatteringphase shift information. The formula-tion of the nuclear forces througheffective field theory yields a series ofFeynman diagrams with an orderparameter that is a ratio of the momen-tum transfer in scattering and amomentum cut-off parameter, usuallytaken to cover the range of scatteringdata up to about 500 MeV. At the thirdorder in the expansion, three-bodyforces appear. This should come as nosurprise as nucleons are not point-likefundamental particles, but are madeup of quarks and gluons. For manyyears we have understood that a three-body force must be active in nuclei as

no two-body interaction, whetherderived from effective field theory orfrom meson theory, has ever been ableto simultaneously fit all nucleon-nucleon scattering data, the deuteronbinding energy, and the masses of thetriton and alpha particle.

A more complete understandingof the nuclear force represents animportant avenue of research for thephysics of nuclei. As Maria Geop-pert-Mayer said in her Nobel Lecture,“[T]he first, the basic approach, is tostudy the elementary particles, theirproperties and mutual interaction.Thus one hopes to obtain knowledgeof the nuclear forces. If the forces areknown, one should, in principle, beable to calculate deductively theproperties of individual nuclei. Onlyafter this has been accomplished canone say that one completely under-stands nuclear structure” [1].

We certainly do understand thenuclear force better today than we didin 1965, which has led to substantialprogress in developing ab initioapproaches to calculate nuclei. Pio-neering efforts using a meson-the-ory-inspired interaction, includingthree-body forces, has been carriedout using Greens Function MonteCarlo approaches. Nuclear spectra

Figure 2. First JUSTIPEN-LACM Meeting, March 2007.



are reproduced from the deuteroninto mass 12 nuclei. Basis expansionmethods have also produced excitingresults in light nuclei. Coupled-clustertechniques are being used to investigatethe nature of closed-shell nuclei into theCalcium and Nickel region. Althoughspace does not permit me to discussthese advances in detail, I believe wehave entered the era of precisionab initio calculations of certain nuclei.

At the same time, we have wit-nessed an increasing understanding ofmedium mass nuclei through advancesin the nuclear shell model. Here effec-tive interactions derived from nuclearspectroscopic information in, forexample, the fp-shell (with 40Ca as aclosed core), have enabled a widedescription and codification of nuclearground and excited state information.Shell model calculations take onvarious forms, including standarddiagonalization and Monte Carloimplementations, and are widely uti-lized by experimental colleagues.

For those nuclei at or very near theneutron drip-line, inclusion of contin-uum single-particle states (scattering

states, resonant states, and the non-resonant continuum) is necessary forthe proper description of these nuclei.Derivation and implementation ofshell-model technology to incorporateGamow single-particle basis states canbe used to describe these very weaklybound systems and opens the door totheoretical investigations of the chal-lenging problems associated with openquantum systems. Coupled-cluster the-ory using Gamow-basis states wasrecently implemented to calculatewidths of and binding energies of theHelium isotopes.

To reach the heavier nuclei weturn to nuclear density functional the-ory (DFT), which utilizes both matterand pairing densities to produceinformation on the properties ofnuclei. The list of topics covered inthis area includes substantial researchon the methods, the forces, extensionsfor excited states, projection to goodquantum numbers, fission mecha-nisms for heavy nuclei, and time-dependent phenomena, all of whichare important for the development ofnuclear DFT.

A comprehensive theory of nucleiwould be incomplete without reac-tion theory, and progress in this arenain light nuclear systems ties nicelywith efforts in ab initio calculations.Recently the Greens Function MonteCarlo collaboration calculated neu-tron-alpha phase shifts and found thatthe three-body force affects these,and No Core Shell Model group cal-culated 7Be(p, γ)8B cross-section as afunction of center-of-mass energy.These efforts point to an interestingfuture for reaction theory in lightnuclei. Improvements in the nucleardensity functional approach shouldalso lead to a more complete descrip-tion of optical potentials for nuclearscattering.

Another line of research involvesunderstanding the simplicities, orsymmetries, found in nuclear spectraand relating those to the underlyingquantum many-body problem of thenucleus. Numerous simplicities innuclear spectra can be described byinvoking symmetry arguments. Theseefforts will be particularly useful inapproaching neutron-rich mid-shellnuclei where symmetries such as X(5)are believed to exist.

Nuclei are produced in stars andnuclear astrophysicists seek to under-stand how nuclear processes haveshaped the cosmos, from the origin ofthe elements, the evolution of stars,and the detonation of supernovae, tothe structure of neutron stars and thenature of matter at extreme densities.The collaborations in this area coverastrophysical observations and, also,astrophysical simulations as nucleardata (and theoretical calculations) areutilized in simulations ranging fromnucleonsynthesis to stellar explo-sions. Sensitivity studies indicate thatcertain nuclear processes are veryimportant for these processes and

Figure 3. The figure shows the nuclei in the N,Z plane over layed withtheoretical approaches being developed to understand all nuclei.



point to the need for experimentalefforts on specific reaction rates.

Conclusion and Perspective In conclusion, the initial years of

JUSTIPEN lead one to believe that theexchange activity will prove to bevery fruitful indeed. JUSTIPENaffords significant opportunity forU.S. and Japanese scientists to collab-orate on numerous projects related toexotic nuclei. Reciprocating visits ofJapanese and U.S. scientists will

enhance our understanding of bothnuclei and bring a broad benefit toboth nations. The major goal ofJUSTIPEN is to deliver an interna-tional venue for research on the phys-ics of nuclei during an era ofexperimental investigations on rareisotopes. We are now at the two-yearanniversary of this effort, and lookforward to a continuing productivescientific endeavor that will enhanceinternational collaborations in theareas of the physics of nuclei and

nuclear astrophysics where unstablenuclei play an important role.

Reference 1. M. Goeppert Mayer, in Nobel Lec-

tures, Physics, 1963–1970, Elsevier,Amsterdam (1972), available at http://nobelprize.org/nobel_prizes/physics/laureates/1963/mayer-lecture.html

DAVID J. DEAN

Oak Ridge National LaboratoryOak Ridge, Tennessee, USA



Compass and the Nucleon Spin Puzzle

The COMPASS Spectrometer The COMPASS (COmmon Muon

and Proton Apparatus for Structureand Spectroscopy) experiment hasbeen in operation at CERN since2002, carrying on an ambitious exper-imental program on the spin structureof the nucleon and on hadron spectros-copy. The spin structure of thenucleon has been investigated byimpinging a 160 GeV/c momentum m+

beam on solid polarized targets. In2002, 2003, 2004, and 2006 a polar-ized deuteron target (6LiD) was used,while in 2007 data were collected on aNH3 polarized proton target. In thisarticle I will focus on the contributionof COMPASS to the problem of thenucleon spin. I will not mention thehadron program, searching for glue-balls and exotics in central productionand diffractive processes, which juststarted in 2008, with a first run with a190 GeV/c momentum pion beam scat-tering off a liquid Hydrogen target.

A worldwide effort, both theoreti-cal and experimental, has beendevoted to the understanding of theorigin of the nucleon spin during thepast twenty years. Excellent reviewsexist on the physics case.1 Here I willtry to outline only the general terms ofthe problem, giving a short account ofour contribution.

The apparatus we have used forthe muon beam program consists of atwo-stage magnetic spectrometer,60 m long, which allows the recon-struction of trajectories and momentaof the incoming and scattered muonsand of the produced hadrons. Chargedparticles are identified by a RICH

(Ring Imaging CHerenkov) counterand by hadron calorimeters. The targetmaterial is contained in two 60-cm-long cells, which are polarized bydynamic nuclear polarization in oppo-site directions, so that data from bothspin directions are recorded at thesame time. Since 2006, a new targetmagnet has been used, increasing theacceptance from ±70 mrad to±180 mrad. Also, the target materialhas been distributed in three cells, andpolarized as + − + or − + −. The fulldescription of the spectrometer can befound in Ref. [3], whereas Figure 1gives an artistic view. Data have beencollected both in the longitudinal tar-get mode (polarization direction paral-lel to the beam) and in the transversemode (target polarization orthogonalto the beam direction).

The “Spin Crisis” Protons and neutrons constitute

99.9% of the material world we live in,but it is fair to say that we still lack afull description of their internal struc-ture. Since the pioneering experimentsat SLAC in the late 1960s, deep inelas-tic scattering (DIS) is the standard tech-nique to investigate the structure of thenucleon. Using polarized lepton beamsand polarized targets the spin structureof the nucleon can be investigated. Ifboth the beam and the target spins arealigned along the direction of the inci-dent lepton, one structure function, g1,can be measured from the cross-sectionasymmetry of the inclusive scattering.In the quark parton model this structurefunction can be written as

where are the differences of the

quark densities with quark spin antipar-allel and parallel to the target nucleonspin. The quantity x is the Bjorken vari-able, the fraction of the nucleon momen-tum carried by the target parton.

Integrating g1(x) from 0 to 1 one

obtains a linear combination of thethree light quarks first moments

. Using additional

information from the neutron beta-decay and from hyperons strangenesschanging decay, which provide two lin-ear combinations for �q’s, (�u−�d)and (�u + �d− 2�s), respectively, it ispossible to extract �Σ = �u +�d + �s.The quantity �Σ can be interpreted asthe contribution of the quarks to thespin of the nucleon, which in generalterms can be written as

In this expression, �G is the contribu-tion of the gluons, and Lq,G are possi-ble contributions from the gluons andquarks angular momenta.

In the simple quark model thethree valence quarks are in an S-state,so Lq = 0. There are no gluons, so that�G = 0 and LG = 0, thus the spin sum-rule is satisfied by �Σ = 1.

The first measurements of polar-ized electron-proton scattering wereperformed at SLAC in the 1980s bythe E80 and E130 Collaborations, andyielded results that were consistentwith expectations. A breakthroughoccurred when the European MuonCollaboration (EMC) at CERNextended these measurements to amuch larger kinematic range, by using

1See, for instance, Ref. [1] for the longitudinalspin; Ref. [2] for the transverse spin.

g x e q xqq121

2( ) ( )= ⋅∑ Δ

Δq x q x q x q( ) [ ( ) ( )] [= + −↓↑ ↓↑ ↑↑

( ) ( )]x q x+ ↑↑

Δ Δq q x dx= ∫ ( )0

1

1

2

1

2= + + +ΔΣ ΔG L Lq G .



a polarized muon beam with an energy10 times higher than at SLAC. In 1988the Collaboration reported [4] that

�Σ = 0.12 ± 0.09(stat) ± 0.14(syst),

that is, a small value, even compatiblewith zero. A major surprise that sooncame to be known as the “spin crisis.”Actually, the inadequacy of the staticquark model should have been real-ized well before the execution of theEMC experiment, but very likely themajor achievements of the quarkmodel had cast a shadow on this point.In particular, the amazing success ofthe static quark model in explaining themagnetic moments of the baryons(three valence quarks in an S-stateSU(6) wave-function, with Dirac mag-netic moment and about 340 MeV/c2

mass) undoubtedly contributed to radi-cate in our minds the idea that the pro-ton spin is carried by the quarks.

Several other polarized DIS exper-iments on the proton, the deuteron,and 3He, have confirmed the EMCresult. All these experiments (includ-ing COMPASS) allow us now to accu-rately determine �Σ, the contributionof both valence and sea quark spins tothe nucleon spin, to be only 30%.Actually, g1(x) and �q(x) are alsofunctions of Q2, the square of the massof the virtual photon that is exchangedin the process, and G(x, Q2) and�q(x, Q2) mix up in the evolutionequations of QCD, so that the extrac-tion of the first moments requires afull QCD fit. However, it was alreadyclear in the mid-1990s that a betterunderstanding of the nucleon spinstructure demanded separate measure-ments of the missing contributions,that is, the gluon polarization �G/Gand Lz. In particular, several theoreti-cal analyses suggested a large contri-bution �G as a solution to the spin

crisis. To single out this contribution, anew experimental approach was neces-sary, namely semi-inclusive DIS withthe identification of the hadrons in thecurrent jet. A flavor tagging procedureallows us to then identify the struckparton, and thus to separately deter-mine �q,�q, and �G. A suggestion toisolate the photon-gluon fusion (PGF)process g*g → qq and measure �Gdirectly had already been put forward afew years before, and implied measur-ing the cross-section asymmetry ofopen charm production in DIS. A newexperiment, with full hadron identifica-tion and calorimetry, therefore seemedto be necessary, and COMPASS wasproposed to CERN in 1996.

The Case for Transversity In parallel to the necessity of direct

measurements of �G/G, semi-inclusiveDIS seemed to be the best tool toinvestigate transverse spin phenom-ena. As a matter of fact, the knowl-edge of the helicity distributions�q(x) and �G does not exhaust thespin structure of the nucleon. It hadbeen realized in 1991 that to fully spec-ify the quark structure of the nucleon at

the twist-two level, the transverse spindistributions �Tq(x) must be added toq(x) and to �q(x) [5].

The definition of �Tq(x) is analo-gous to that of �q(x), but it refers totransversely polarized quarks in atransversely polarized nucleon. Sincerotations and Lorentz boost do notcommute, helicity and transversity areexpected to be different. �Tq(x) givesa measure of the correlation betweenthe transverse quark spin and thetransverse nucleon spin. Being chiral-odd, transversity cannot be measuredin inclusive DIS (the hard processconserves chirality) but only in a pro-cess in which it combines with anotherchiral-odd quantity.

Transversity can be extracted frommeasurements of single-spin asymme-tries in cross-sections for semi-inclusiveDIS (SIDIS) of leptons on trans-versely polarized nucleons, in whichhadrons are also detected in the finalstate. In this process the second chiral-odd object is the fragmentation func-tion. It was conjectured in 1993 [6]that there could be a correlationbetween the spin of a transverselypolarized quark and the kT of the had-ron into which the quark fragments.

Figure 1. Artistic view of the COMPASS spectrometer.



This part of the fragmentation func-tion is usually named Collins function( ). In the hadronization of atransversely polarized quark a non-zero Collins function would beresponsible for a left–right asymmetryof the hadrons with respect to theplane defined by the quark spin andmomentum directions. In SIDIS on atransversely polarized nucleon, a non-zero , in conjunction with �Tq,would cause a left–right asymmetry ofthe resulting hadrons with respect tothe plane defined by the struck quarkspin (i.e., the nucleon spin, reflectedabout the normal to the scatteringplane) and the virtual photondirection. In this case the measurableasymmetry, the so-called Collinsasymmetry, AColl, is the convolutionof �Tq and of , and has origi-nally been suggested as a possible wayto measure transversity.

The transversity distribution andthe Collins function are two examplesof correlations (quark spin andnucleon spin, quark spin and fragmen-tation hadron kT respectively), whichrecently have been recognized asbeing crucial for understanding thespin structure of the nucleon in termsof the quark and gluon degrees of free-dom of QCD. Particularly importantare the transverse momentum depen-dent (TMD) parton distribution andfragmentation functions. These func-tions are time-reversal odd (T-odd)functions, and as such are of particularimportance as they can generate sin-gle-spin asymmetries. Large single-spin asymmetries in hadron-hadroncollisions have been known for manyyears, and have been measured evenrecently at RHIC, and a large-scaleeffort is ongoing to provide in theframework of QCD a unified descrip-tion of both the SIDIS and the hadron-hadron transverse spin asymmetries.

The Sivers distribution function,�T

0q(x) [7], is probably the mostfamous TMD distribution function.Allowing for a correlation between thenucleon spin and the intrinsic KT of thequark, the distribution of the hadronsresulting from the quark fragmentationmight exhibit a left–right asymmetry(usually called the “Sivers asymmetry”ASiv) with respect to the plane definedby the nucleon spin and the virtual pho-ton direction. In this case the observableis the product of the Sivers DF and theFF. Measuring SIDIS on a transverselypolarized target allows the Collins andthe Sivers effects to be disentangled.

Investigation of the transverse spinphenomena in SIDIS is complementaryto the investigation of longitudinal spinphenomena. A spin sum-rule can also bewritten for the transverse spin case [8]

The gluon contribution being absent inthe transverse case, from the knowl-edge of direct information on the sizeof the orbital angular momentum canbe derived.

COMPASS Results onLongitudinal Spin

In this short report I will concentrateonly on the measurements of g1 and of�G/G, and will skip all the other resultsCOMPASS has obtained in the longitu-

dinal target polarization mode (from theflavor separated helicity distributions, toL-physics and to vector meson-physics).

To directly measure �G two pro-cedures have been followed to tag thePGF process. The first one consists inselecting open-charm events, whichprovide the purest sample of PGFevents, but at a low rate. Open-charmevents are identified by reconstructingD0, D0, D*+ and D*− mesons fromtheir decay products. The full 2002–2006 data set has been analyzed andthe preliminary results are given inTable 1, where m2 is the QCD scale.

A second option is to select eventswith two high-pT hadrons (withrespect to the virtual photon direc-tion), as tags of the two jets from thehadronization of the qq pair. The latterprocedure provides much larger statis-tics but leaves a significant fraction ofbackground events in the selected sam-ple, which has been estimated withsophisticated MonteCarlo simulations.DIS events (Q2 >1 (GeV/c)2) and lowQ2 events are considered separately,and different generators are used asreliable models for the interaction ofthe virtual photon with the nucleons.

Results from the Q2 < 1 (GeV/c)2

data collected in the years 2002–2003have already been published [9]. Apreliminary value for �G has beenextracted from the whole set of 2002,2003, 2004 deuteron data, and it isgiven in Table 1.

�T0 Dq

h

�T0 Dq

h

�T0 Dq

h

1

2

1

2= +∑ ΔTq qq L .

Table 1. COMPASS results for the direct measurement of �G/G.

Method �G/G Statistical error

Systematic error <xg>

<m2> GeV/c2

Open charm − 0.49 ± 0.27 ± 0.11 0.11 13

high-pT events, Q2 > 1 + 0.08 ± 0.10 ± 0.05 0.082 3

high-pT events, Q2 < 1 + 0.016 ± 0.058 ± 0.055 0.085 3



A similar analysis has been per-formed for the SIDIS events (Q2 > 1(GeV/c)2). A preliminary analysis ofthe data collected in 2002, 2003, and2004 has provided the results shownin Table 1.

The COMPASS experiment hasalso measured with high precision thelongitudinal virtual photon asymmetryAd

1 of the deuteron. Figure 2 gives theCOMPASS measurement, whichrefers to 2002, 2003, 2004 and hasbeen recently published [10], com-pared with previous measurements[11–14]. At small x (x < 0.03) theCOMPASS data exhibit errors that areconsiderably smaller than the previousSMC results, which is of great rele-vance when extrapolating the data tox=0 to evaluate the first moment of g1.

From Ad1 the structure function gd

1

of the deuteron is obtained

where Fd2 is the spin-independent deu-

teron structure function and R is theratio of longitudinal and transverse

photoabsorption cross-section. Usingall the available gd

1 data, we haveperformed a QCD fit [10] in the MS

normalization scheme and obtainedfor the singlet moment at Q2=3 (GeV/c)2

�Σ = 0.30 ± 0.01(stat) ± 0.02(evol).

The same fit provides estimates for�G(x) and for its first moment. Twodifferent solutions are equally accept-able, one with �G(x) > 0 and the otherwith �G(x) < 0. Figure 3 shows thedistributions of the gluon polarizationthat results from the two fits. The con-clusion from the fit is that the firstmoment of �G(x) is of the order of0.2–0.3 in absolute value atQ2 = 3(GeV/c)2.

Also shown in Figure 3 are ourdirect measurements from Table 1, aswell as the published results [15] andthe recent preliminary value [16] fromthe HERMES Collaboration, and the

Figure 3. Distribution of the gluon polarisation �G(x)/G(x) at Q2= 3(GeV/c)2

for the two QCD fits with �G > 0 and �G < 0 performed by the COMPASSCollaboration. The data points show the measured values from SMC [17],HERMES [15, 16], and COMPASS (Table 1).

Figure 2. The asymmetry Ad1 as measured in COMPASS [10] and previous results

from SMC [11], HERMES [12], SLAC E143 [13], and E155 [14] at Q2>1 (GeV/c)2.

gF

x RAd

dd

12

12 1=

+( )



result from the SMC Collaboration[17]. The picture that emerges clearlyfavors small values of �G, a conclu-sion supported also by the recent mea-surements at RHIC.

COMPASS Results on Transverse Spin

The COMPASS experiment hasmeasured for the first time single had-ron transverse spin asymmetries in DISof high energy muons on deuterons andprotons, scattering the 160GeV/cmuon beam on transversely polarized6LiD and NH3 targets. Also in thiscase, several asymmetries have beeninvestigated, in particular for a twohadron system, exclusive r, and lhyperons, but in this short report I willmention only the results for Collinsand Sivers effects.

Collins asymmetries definitely dif-ferent from zero have been reported

for a few years by the HERMES Col-laboration, measuring semi-inclusiveDIS events on a transversely polarizedproton target, providing evidence thatboth the transversity PDF and the Col-lins FF are different from zero. Inde-pendent evidence that the Collinsmechanism is a real measurable effecthas come from the recent analysis ofthe BELLE Collaboration. Our mea-surements on the deuteron do notshow any appreciable effect, and allthe measured asymmetries are com-patible with zero, as apparent fromFigure 4, which shows our latestresults for p± [18] from the 2003 and2004 runs (the Collins and Siversasymmetries on the deuteron for non-identified hadrons from the 2002,2003, and 2004 data have alreadybeen published [19, 20]).

The deuteron being isoscalar, thenull result from COMPASS can beunderstood in terms of cancellation

between �Tu and �Td. A few analy-ses aiming at the extraction of thetransversity distributions have alreadybeen performed, and all the observedphenomena can be described in a uni-fied scheme. In Figure 4 the results ofour measured deuteron asymmetriesare compared with the results of themost recent global analysis ofAnselmino et al. [21] which uses theCollins asymmetries from HERMES(proton) and from COMPASS (deu-teron), and the e+ e− → hadrons datafrom BELLE to fit the valence u- andd-quark distributions �Tuv, �Tdv, andthe Collins functions forfavored and unfavored fragmentation(9-parameter fit). In Figure 5 the

�T0 Dq

h

Figure 5. The transversity distributions�Tqv for the u- and d-quarksextracted with a global analysis of allthe existing data by M. Anselminoet al. (lower red curves). The dottedcurves are the corresponding helicitydistributions and the blue curvesindicate the so-called Soffer bound.

Figure 4. COMPASS results for p± Collins asymmetries [18] on deuteron fromthe 2003 and 2004 runs compared with the fit results of the global analysis ofAnselmino et al. [21].



extracted transversity distributions�Tqv for the u- and d-quarks are plot-ted and compared to the correspond-ing helicity distributions. This is thefirst time the transversity distributionsare extracted with a global analysis ofall the existing data, but it is alreadypossible to note that the transversitydistributions (in particular the d-PDF)are considerably smaller than the cor-responding helicity distributions, anddo not saturate the so-called Sofferbound. Most rewarding is the com-parison of our very recent prelimi-nary results of the Collins asymmetryof the proton [22] with the expecta-tions from the same global analysis.The comparison between our newdata and the predictions of Anseminoet al. is shown in Figure 6. The agree-ment is very good, and a clear sign ofthe soundness of the physics which isbehind it.

We have also measured the Siv-ers asymmetry. All the asymmetrieswe have measured on the deuterontarget are small, if any, and compati-ble with zero. On the other hand, theHERMES p+ data on a proton targethave also provided convincing evi-dence that the Sivers mechanism isat work, and that is differentfrom zero. The approximately zeroSivers asymmetries for positive andnegative hadrons observed in COM-PASS require ∼ −�T

odv, a rela-tion that is also obtained in somemodels, and which anyhow has asimple physical interpretation if theSivers distortion of the PDF of thenucleon is associated with theorbital angular momentum of the u-and d-quarks. The preliminaryresults from our proton data [22]suggest Sivers asymmetries that arecompatible with zero both for nega-tive hadrons and for positive had-rons. The result for positive hadron

is only marginally compatible withthe finding of HERMES, and has tobe understood.

Is the Nucleon Spin Puzzle Solved? Twenty years after the EMC mea-

surement, it is fair to say that thanks toa huge theoretical and experimentaleffort many things have been under-stood:

a. The original measurement sug-gested that �Σ might have beenas small as zero. After a newgeneration of experiments weknow that it is not so; �Σ is mea-sured to be 0.3 with good preci-sion. Accurate comparisons withthe predictions of sum-rules (inparticular with the fundamentalBjorken sum-rule) have beenpossible. The interconnectionbetween �Σ and �G and the

necessity of full QCD analysishave been clearly established.

b. The comparison with the staticquark model was misleading. Evenstarting with three valence quarks inan S-state, the Melosh rotation,which gives the connection betweenthe spin states in the rest frame andin the infinite momentum frame,introduces a nontrivial spin structureand correlations between quark spinand quark angular momentum;

c. The possibility that most of themissing spin be carried by thegluon seems ruled out by thepresent direct measurements of�G. The precision on �G willimprove in the next years thanks tothe combined analysis of the DISdata and of the polarized proton-proton data coming from RHIC,but without a dedicated e-p col-lider it seems difficult to assesswith high accuracy which fraction

�0T uv

�0T uv

Figure 6. COMPASS preliminary results of the Collins asymmetry of the protonfrom 2007 data [22]. The curves are the expectations from the global analysisof Ansemino et al. [21].



of the nucleon spin is due to thegluon and which is due to theorbital momentum.

d. New possibilities to understand thespin structure are offered by theinvestigation of transverse spineffects. New properties of matterhave been unveiled. The Collinseffect is there and precise measure-ments of transversity and of thequark orbital angular momentumare at hand.

As it has always been since the dis-covery of Stern and Gehrlach in 1921,the history of spin is a history full ofsurprises.

References 1. S. D. Bass, Rev. Modern Phys., 77 (2005),

1257. 2. V. Barone et al., Phys. Rep. 359 (202), 1.

3. COMPASS Collaboration, P. Abbonet al., Nucl. Instrum. Meth. A 577(2007), 455.

4. EMC Collaboration, J. Ashman et al.,Phys. Lett. B206 (1988), 364; Nucl.Phys. B328 (1989), 1.

5. R. L. Jaffe and X. Ji, Phys. Rev. Lett.67 (1991), 552.

6. J. Collins, Nucl. Phys. B396 (1993), 161. 7. D. Sivers, Phys. Rev. D41 (1990), 83. 8. B. L. G. Bakker, E. Leader, and T. L.

Trueman, Phys. Rev. D70 (2004),114001.

9. COMPASS Collaboration, E. S. Ageevet al., Phys. Lett. B633 (2006), 25.

10. COMPASS Collaboration, V. Y. Alex-akhin et al., Phys. Lett. B647 (2007), 8.

11. SMC Collaboration, B. Adeva et al.,Phys. Rev. D58 (1998), 112001.

12. HERMES Collaboration, A. Airapetianetal., Phys. Rev. D71 (2005), 012003.

13. E143 Collaboration, K. Abe et al.,Phys. Rev. D58 (1998), 112003.

14. E155 Collaboration, P. L. Anthonyet al., Phys. Lett. B463 (1999), 339.

15. HERMES Collaboration, A. Airapetianetal., Phys. Rev. Lett. 84 (2000), 2584.

16. D. Hasch, HERMES Collaboration.,AIP Conf. Proc. 915 (2007), 307.

17. SMC Collaboration, B. Adeva et al.,Phys. Rev. D70 (2004), 012002.

18. COMPASS Collaboration, M. Alek-seev et al., CERN-PH-EP/2008-002,arXiv:0802.2160 hep-ex..

19. COMPASS Collaboration, V. Y.Alexakhin et al., Phys. Rev. Lett. 94(2005), 202002.

20. COMPASS Collaboration, E. S. Ageevet al., Nucl. Phys. B765 (2007), 31.

21. M. Anselmino et al., Phys. Rev. D75(2007), 054032 and PKU-RBRCWorkshop on Transverse Spin Physics,Peking, June 30–July 4, 2008.

22. S. Levorato, COMPASS Collaboration,Transversity 2008, Ferrara, Italy, May28–31, 2008, arXiv:0808.0086 hep-ex.

FRANCO BRADAMANTE

University of Trieste and TriesteSection of INFN, Italy

impact and applications


Industrial PET at Birmingham

In the 75 years since the firstobservation of the positron in cosmic-ray showers, positron emissiontomography (PET) has developed intoone of the most powerful diagnostictools in medicine. For clinical studies,a fluid of interest is labeled with apositron-emitting radioisotope andintroduced into the body. By detectingthe pairs of back-to-back 511 keVg-rays produced in positron-electronannihilation, a PET scanner builds upa quantitative 3D map of the concen-tration of this fluid, revealing itsuptake by individual organs. Forexample, a labeled form of glucose isused to map metabolic rate and iden-tify tumors (which metabolize glucoserapidly).

A similar approach can be used tostudy flow inside engineering sys-tems. The 511 keV g-rays are highlypenetrating (50% are transmittedthrough 11-mm steel) so non-invasivemeasurements can be made on realindustrial equipment. The potential ofPET for such studies has beenexplored and developed at the Univer-sity of Birmingham for over 20 years.Unfortunately PET is a slow technique,

requiring measurement of millions ofindividual g-ray pairs to reconstruct anaccurate 3D image, which makes itunsuited to observing the dynamics offast flows. For many applications, thealternative technique of positron emis-sion particle tracking (PEPT), devel-oped at Birmingham, proves moreuseful. In PEPT, a single, radioac-tively labeled tracer particle is trackedas it moves around inside the systemunder study. The particle’s instanta-neous location is determined by trian-gulation using a small number ofdetected pairs of back-to-back g-rays(Figure 1). In principle just twodetected pairs provide an estimate oflocation, since each defines a linepassing close to the tracer position. Inpractice more are required to obtain anaccurate location, especially as manyof the detected pairs are corrupt, forexample because one or both of the g-rays has scattered prior to detection.Given a large enough sample, thecluster of useful lines that converge onthe tracer position can be distin-guished from the broad background oflines due to corrupt pairs. An iterativealgorithm is used, which starts with asample of typically 100 pairs, calcu-lates their centroid, then discards theoutliers and recalculates using just theremaining pairs. This process contin-ues until all corrupt pairs have beendiscarded.

Figure 2 shows an example ofPEPT data, following the motion of asingle particle within a fluidized bed.Such systems are widely used inindustry for processing granular mate-rial: if gas (often air) is blown upwardthrough a bed of particles with suffi-cient velocity the particles becomesuspended and the bed moves around

like a fluid. The figure shows (a) thetrack of the particle over a period of afew seconds, (b) the “occupancy” dis-tribution representing the fraction ofthe run time during which the particlewas found in each region, averagedover a period of many minutes, and (c)its average velocity at each position.Assuming that the tracer’s behavior isrepresentative of all the particles in thebed, the time-averaged quantities (b)and (c) should describe the averagenumber density of particles in the bedand their average velocity field. Aswell as studying granular material,PEPT can also be used to study thebehavior of viscous fluids, by intro-ducing a small neutrally buoyant parti-cle as a flow follower. Routinely atBirmingham, the tracer is located 500times per second (so that a particlemoving at 5 m/s is observed at inter-vals of 10 mm along its path) to a pre-cision of around 1 mm.

This work dates back to the early1980s when Mike Hawkesworth atBirmingham was asked by colleaguesfrom Rolls Royce if he could find away of imaging the lubricant distribu-tion inside an operating aero-engine.Hawkesworth realized that PET,which was then just starting to be usedin medicine, could in principle pro-vide the answer. Simultaneously,Eddie Bateman and his team at theRutherford Appleton Laboratory hadbeen developing a “positron camera”based on a pair of gas-filled multiwireproportional chambers (MWPCs),which they hoped would provide aninexpensive detection system for med-ical PET. Instead, this system wasdeveloped into a robust camera forperforming engineering PET. Thecamera became operational in 1984,

Figure 1. Basis of PEPT: tracerparticle is located using a smallnumber of back-to-back g-ray pairs.



and shortly afterward was successfullyused to measure PET images of radio-actively labeled lubricant inside asmall jet engine operating at fullpower on a testbed.

The link with Rolls Royce endedaround 1990, but the Birminghamgroup continued to explore the use ofPET in engineering. An early applica-tion was to study motion in fludizedbeds, and PEPT was first developed asa way of observing the motion of largeparticles within such a bed. In the sub-sequent 15 years the technique hasbeen refined, and techniques havebeen developed for labelling a rangeof tracer particles with sizes down to100 mm. PEPT has been used by alarge number of university groups andby researchers from industries includ-ing petrochemicals, pharmaceuticals,food, and minerals processing, tostudy processes involved in the manu-facture of products ranging from phar-maceutical tablets to canned food andfrom washing powder to ice cream.

The original MWPC positron cam-era performed reliably for over 15years. During this period, the use ofPET in medicine became more wide-spread, and equipment manufacturers

developed a variety of off-the-shelfPET detector systems, includinggamma camera PET systems that weremarketed as multipurpose imagingsystems for nuclear medicine. In 1999we replaced the MWPC camera withone of these systems, comprising apair of gamma camera heads operatingin coincidence. Each head consists ofa sheet of sodium iodide scintillatorbacked by an array of 55 photomulti-plier tubes (PMTs) that detect theflash of light produced by a g-rayinteracting in the scintillator and local-ize this to within a few mm. This sys-tem is ideal for PEPT, with an opengeometry able to accommodate largerigs (Figure 3). It can record up to100 k g-ray pairs per second, com-pared to a maximum of 5 k per secondfrom the MWPC system.

Dedicated medical PET scannersgenerally use a different approach,comprising hundreds of small, high-efficiency detectors, mounted in ringsabout the patient. Such scanners offersignificantly higher sensitivity andcount rate than a gamma-camera PETsystem, but the restricted field of viewis unsuitable for studying large engi-neering rigs. Fortuitously, in the last

few years the world of medical PEThas been revolutionized by the intro-duction of combined PET/CT scan-ners, in which a near-simultaneous X-ray image of a patient’s anatomy canbe measured and superimposed on thefunctional PET image. As a result, anumber of older PET centers decidedto replace their existing PET scannerswith PET/CT systems, and Birming-ham was able to acquire their oldscanners. Like this, we have recentlyobtained four complete PET scannersas well as components from two oth-ers, and have reconfigured them forour use.

The detectors inside these scannersare grouped in modules, each with itsown electronics. A typical scannercontains 32 such modules. A flexiblePEPT system can be constructed sim-ply by arranging the modules in a dif-ferent geometry. Whereas for PET it isimportant to sample g-rays uniformlyaround a complete circle, for PEPT

Figure 3. The gamma-camera systembeing used in a PEPT study ofa fluidized bed.

Figure 2. Example of PEPT data, from a spouted fluidized bed: (a) short sectionof particle track, (b) occupancy and (c) velocity field.



any arrangement of detectors can beused provided the tracer is always inline between at least one pair. Theresulting “modular positron camera”has the advantage that it is transport-able, so that PEPT studies can be per-formed outside the lab. In the last twoyears, this system has been used forseveral applications, including observ-ing single particle motion inside alarge fluidised bed at BP’s Hull site(230 km from Birmingham) andstudying the casting of liquid alumin-ium into molds in the UniversityFoundry (Figure 4). When the detectormodules are packed closely togetherthis system can detect up to 4 M g-raypairs per second, allowing very accu-rate tracking of fast-moving tracers.

Not all the work at Birminghamuses PEPT. Conventional PET hasrecently been used to study the blendingof powders for pharmaceutical formu-lation. Because each PET scan takesseveral minutes, this study was carriedout in stop/start mode: a small amountof labeled powder was added to themix and imaged, the blender was runfor a few seconds and then stopped foranother image, and so on. PET is espe-cially suited for observing very slowflows, and over the years we have per-formed a number of studies on flow ofliquid or gas through geological sam-ples. Using components from one ofthe medical scanners, we have alsobuilt what we believe to be the world’slargest PET scanner: a ring of 128detector blocks with an inner diameterof 2.3 m.

Positron emitting isotopes are gen-erally produced using a cyclotron.Birmingham has a long history ofdeveloping and operating cyclotrons,beginning with the Nuffield Cyclo-tron, which operated from 1948 until1999. The PET work was started withthe aid of radioisotopes produced by

the Radial Ridge Cyclotron, whichcommenced operating in 1960, but bythe late 1990s this cyclotron wasbecoming increasingly unreliable, andthe opportunity was taken to replace itwith a more modern cyclotron. Thepresent Scanditronix MC40 Cyclo-tron was purchased second-hand fromthe VA Medical Center, Minneapolis,at the beginning of 2002, was movedto Birmingham and recommissionedduring 2002–2004, and has been fullyoperational since March 2004.During 2005, we extended the layoutby acquiring the switching magnetfrom the former Vivitron accelera-tor, which allows the beam to beswitched between 12 independenttarget stations.

The MC40 is a flexible researchcyclotron, delivering variable energybeams of hydrogen and helium ions

with maximum energies of 40 MeV(protons or alphas), 20 MeV (deuter-ons), and 53 MeV (3He). It has provedextremely reliable, and in addition toproducing the tracers required by thePositron Imaging Centre it is used fora variety of research purposes, includ-ing surface activation of componentsfor wear testing, and measuring radia-tion effects on electronics destined foruse in space. The MC40 cyclotronalso produces 81Rb daily for sale tohospitals across the United Kingdom.

The activity required in a PEPTtracer depends on the tracer speed, thesize of the system (detector separa-tion), and the extent of g-ray attenua-tion in surrounding material. In acompact low-mass system accuratehigh speed tracking can be achievedusing a tracer with an activity ofaround 10 MBq, but for a large dense

Figure 4. The modular positron camera being used in a PEPT study of liquidaluminium casting. The detector modules are mounted inside protective boxesand arranged in four orthogonal stacks.



system (e.g., a stirred water tank)activities up to 40 MBq are optimal.

Just as in medical PET, most stud-ies at Birmingham use the radioiso-tope 18F, which has a half-life of 110minutes, but whereas medical PETcenters generally produce 18F byproton irradiation of water, which isisotopically enriched in 18O, atBirmingham the alternative produc-tion route using 3He on natural oxy-gen is used. In this way, everydaymaterials such as glass or aluminabeads can be directly activated foruse as PEPT tracer particles. Targetscontaining oxygen are irradiated witha 36 MeV 3He beam, producing 18Fthrough the reactions 16O(3He, p)18Fand 16O(3He, n)18Ne ⇒18F. In manycases, the target is water (naturalwater, not H2

18O) so that the result isa very dilute solution of radioactivefluoride, which must then be attachedto the particle of interest. A range of

techniques has been developed forlabeling particles including poly-mers, plant seeds, catalysts, minerals,coal, metals, and microcrystallinecellulose down to 100 mm in size.Tracer particles produced in this waysurvive well in dry conditions or inorganic solvents, but in an aqueousenvironment the activity tends toleach away rapidly. A crude solutionto this problem is obtained by paint-ing the surface of the tracer afterlabeling, thus sealing the activityinside. A better approach is to use acationic radionuclide such as 61Cu(half-life 3.4 hours) or 66Ga (9.3hours), which binds more irreversiblyto particle surfaces.

Looking ahead, we consider thatPET and PEPT may be of value innumerous untried fields. It’s surpris-ing what can be achieved using sec-ond-hand equipment (cyclotron andPET scanners)!

Acknowledgments I thank all the colleagues who have

worked with me on these projects overthe years, in particular Xianfeng Fan,Andy Ingram, and Jonathan Seville,and I acknowledge with gratitude thecontinuing financial support fromEPSRC.

DAVID PARKER

Positron Imaging Centre,School of Physics and Astronomy

University of Birmingham

meeting reports


The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13

The 13th International Conferenceon Capture Gamma-Ray Spectroscopyand Related Topics, called CGS13 forshort, was held from Monday, August25 to Friday, August 29 at the Instituteof Nuclear Physics of the Universitätzu Köln, with Prof. J. Jolie as thechairman. This conference, of ratherwide scope, already has a longstand-ing tradition, going to 1969, whenthe first edition was organized atStudsvik, Sweden, starting in Petten(the Netherlands) in 1974, Brookhaven(USA) in 1978, Grenoble (France) in1981, coming into a 3-year cyclesince then. The places the meetingwas held onward were Knoxville(USA) in 1984, Leuven (Belgium) in1987, Asilomar (USA) in 1990,Fribourg (Switzerland) in 1993,Budapest (Hungary) in 1996, SantaFe (USA) in 1999, Prague (CzechRepublic) in 2002, and Notre-Dame(USA) in 2005. The tradition ofalternating on both sides of theAtlantic Ocean, with a 3-year inter-val, will continue also this time. Atthe special lunch meeting of theAdvisory and Program Board, anunanimous decision was made tohave the next meeting in the series,that is, CGS14, at the University ofGuelph, moving to Canada for thefirst time. The organization will betaken up by Prof. P. Garrett and alocal organizing team.

The series of CGS conferences ischaracterized by a broad range oftopics encompassing Nuclear Struc-ture, covering most recent develop-ments in both experimental andtheoretical research. Many talksshowed the presence of a strong

synergy of recent experiments in vari-ous fields of nuclear physics withrecent advances in state-of-the-artshell-model methods, nuclear mean-field and beyond approaches alsoinvoking the importance of symme-try concepts as a guiding principle tounderstand the atomic nucleus.Nuclear Reactions including thestudy of statistical properties ofnuclei formed a recurring theme inthe present edition of CGS13. Tradi-tionally, Nuclear Astrophysics takesa particularly strong position in theseries of meetings and this wasagain so in Köln, strongly emphasiz-ing recent experimental work andpointing toward the need of the bestpossible input from theorists andnew theoretical developments. Timehas also been devoted to have a cou-ple of sessions on Nuclear Data. Theconference always has been theplace where much attention andinterest is given to new experimentaltechniques and facilities, covering awhole range from new detector sys-tems, development of new radioac-tive beams, over the use of neutrons(cold neutron beams, neutronsources). Also, sessions on practicalapplications (covering material sci-ence, imaging, interface with otherscientific disciplines such as chem-istry, biology, . .) were included atthe CGS13 conference. A particu-larly attractive part comes from thefact that neutrons can play a veryimportant and fundamental role inthe study of basic physics. The ses-sion on Fundamental Physics tookup that line of research and excitingnew results were presented.

The conference in Köln was a verylively example of presentations, dis-cussions covering the overlappingregions between various excitingdomains in the physics of atomicnuclei, and their study through the useof a large set of complementaryprobes. Due to the large number ofparticipants (164 registered physicistsrepresenting 28 different countries)and the many high-quality abstractssubmitted, on Tuesday, Wednesday,and Thursday morning, parallel ses-sions had to be organized next to the16 plenary sessions. With the two lec-ture rooms very close to each other,the movement from one to the otherwent rather smoothly.

Among the participants, there wasa very large fraction of young gradu-ate, postdoc, and junior staff peoplepresent. At the same time, it is goodto mention that Till von Egidy of theTechnische Universität Münich wasthe one physicist present whoattended all 13 editions of the CGSconference.

The program was densely packedand thus the conference trip onWednesday afternoon was very muchwelcome. The trip went first by bus tothe beautiful city of Linz, south ofKöln, where a guided tour passedthrough the narrow alleys of thismedieval little town. The way backwent relaxingly and with fine weatherby boat on the river Rhine, passingthrough the beautiful region near BadHonnef and Köningswinter (close tothe “Siebengebirge“). The early nightwas coming with the boat arrivingnear to the illuminated Dom in theheart of Köln.

meeting reports


A poster session was organizedin the late afternoon on Tuesday.This poster session sought the verybest poster(s) presented by graduatestudents and postdoctoral fellowswith an award of 500 Euro. The bestposter for the ”the Founder’sAward,” an award that was inaugu-rated in honor of the memories ofthe late Jean Kern, SubramanianRaman, and Gabor Molnar, all ofwhom played a major role in estab-lishing thrust and growth of theearly meetings into a major interna-tional conference, had to be selectedamong a large number of high-quality contributions. The selectioncommittee— H.Börner (ILL Greno-ble), F. Käppeler (Forschungszen-trum Karlsruhe), and K. Heyde

(Univ.Ghent)—ended up splittingthe prize among two very fine con-tributions. One half went to a start-ing graduate student from theUniversity of Köln, Linus Better-mann, with a poster on mixed-symmetry states. The other half wasgiven to Steven Pain, a postdoctoralfellow working at Oak-RidgeNational Laboratory (ORNL), witha contribution on the developmentof the ORRUBA Silicon DetectorArray.

A memorable event was the con-ference dinner, on Thursday evening,held at the “Imhoff Schokoladenmu-seum.” This event gave rise to the pos-sibility of socializing in a relaxedatmosphere among the many partici-pants, and this over a great buffet and

fine wines from the Baden region(Kaiserstuhl).

The local organizing team is to becongratulated for the impeccable orga-nization of this 13th edition of the con-ference: not only was a scientificprogram of very high quality arranged,but the flow throughout the five-dayconference ran smoothly indeed in thespacious Physics building, with ampleroom for computing, having discus-sions, and taking time at coffee breakswith cake and cookies. CGS13 willdefinitely go into history as a worthypartner of this gallery of conferences.

KRIS HEYDE

Department of Subatomicand Radiation Physics

University of Ghent(Belgium)

Hadron Physics Summer School 2008 More than 80 graduate and

advanced undergraduate students from14 countries and 4 continents partici-pated in the Hadron Physics SummerSchool HPSS2008 held at Physikzen-trum Bad Honnef, Germany, August11–15, 2008 (Figure 1). Similar to thepreceding COSY Summer School(CSS) 2002, 2004, and 2006, thisschool consisted of lectures and work-ing groups on theoretical, experimen-tal, and accelerator aspects. The focuswas on current issues in hadron phys-ics with emphasis on the latest pro-grams at the accelerators COSY(Jülich) and ELSA (Bonn), also fea-turing future FAIR projects likeHESR/PANDA and PAX. During thevery successful school, the studentswere given a guided tour to the CoolerSynchrotron COSY at Jülich Fors-chungszentrum.

The HPSS2008 was jointly orga-nized by scientists working at theNuclear Physics Institute (http://www.fz-juelich.de/ikp) of the Jülich Centerfor Hadron Physics at Jülich Forschung-szentrum and by the DFG TransregioTR 16 (Subnuclear Structure of Matter,http://sfb-tr16. physik.uni-bonn.de/) of

the Universities Bonn, Bochum, andGiessen. In addition, the HPSS2008 wassponsored by DAAD (German Aca-demic Exchange Service) and DPG(Deutsche Physikalische Gesellschaft),making the participation of youngmotivated students into this challengingenterprise possible.

Figure 1. Participants of HPSS2008 in front of Physikzentrum Bad Honnef.

meeting reports


It is intended to conduct the HPSSevery second year. The series will besupplemented by lecture weeks in thealternate years, which will consist ofinvited lectures and student contribu-tions. The lecture weeks are self-

contained and will also be an excellentopportunity for graduate students andearly post-graduates to deepen theknowledge gained at HPSS.

For more detailed information,see:\\http://www.fz-juelich.de/ikp/hpss2008/.

FRANK GOLDENBAUM

FZ Jülich

news and views


BEPC-II/BES-III Complex

On late Saturday afternoon July19, researchers at the Chinese Acad-emy of Science’s Institute of HighEnergy Physics in Beijing producedfor the first time collisions in theupgraded BEPC-II electron positroncollider that were observed in itsbrand new associated detector, calledBES-III. Although BEPC-II and BES-IIIhad already been carefully tested sepa-rately, this was the first time theyoperated together. These first colli-sions represent a major milestone ofthis project, which involved eightyears of planning and construction.

When it is fully operational, theBEPC-II/BES-III complex will be theworld’s premier facility for studyingthe properties of particles that containa charmed quark (c-quark), the fourthof an assortment of six differentquarks that physicists have identifiedas the most fundamental buildingblocks of matter. In BEPC-II,

c-quarks, which have a mass that isabout 3,000 times that of the electron,are produced together with theirequal-mass antimatter counterpart,anti-charmed quarks (c-quarks), inhead-on collisions of high energyelectrons and anti-electrons (famil-iarly known as positrons). In thesecollisions, the electron and positronannihilate each other and in the pro-cess their energy is converted into themassive c- and c-quark pair in accor-dance with Einstein’s famous relationE = mc2.

To accomplish this, the BEPC-IIteam confines a tightly bunched clus-ter of approximately 50 billion elec-trons inside a vacuum tube thatthreads through a ring of powerfulelectro-magnets that maintains theelectron bunch in a nearly circularorbit. Likewise a similar “bunch” ofpositrons is made to counter-rotate inan identical second ring of magnets.

The two bunches, which have a verti-cal profile of only about five mil-lionths of a meter, are made to crosseach other in the center of the BES-IIIdetector. Occasionally, an electron inone bunch hits a positron in the otherbunch head-on and the two particlesannihilate each other to produce a pairof particles: one containing a c-quarkand an associated one that contains ac-quark. These so-called charmed par-ticles rapidly decay into more conven-tional particles like p- and K-mesonswhose energies and velocities are pre-cisely measured in the BES-III spec-trometer. From these measurements,the properties of the parent charmedparticles can be deduced.

BEPC-II is a major upgrade ofIHEP’s previous collider BEPC. Themajor change has been the addition ofa second ring of magnets that allowsthe electron and positron beams to bestored separately. In BEPC, the elec-trons and positrons shared the samevacuum tube in a single ring of mag-nets, and this arrangement couldaccommodate only a single buncheach of electrons and positrons,thereby limiting the rate at whichinteresting particles are produced. Thetwo separate rings of BEPC-II willallow for 93 bunches in each ring. Inaddition, BEPC-II has many otherimprovements including a more pow-erful injection accelerator that pro-duces the high energy electrons andpositrons, and an extensive use ofsuperconducting technology, both forthe acceleration and magnetic focusingof the stored electron and positronbeams. The net effect of all of theseimprovements will be a more thanhundred-fold increase in the collisionrate. Figure 1. The BESIII detector in the interaction region of BEPCII.

news and views


The BES-III detector is completelynew with a number of major improve-ments over its predecessor, BES-II.These include its huge superconduct-ing magnet, which produces a mag-netic field throughout the detector thatis about 20,000 times stronger than theEarth’s magnetic field. This strongmagnetic field deflects charged parti-cles as they traverse the detector andby measuring the amount of deflectionresearchers can make precision mea-surements of the particles’ velocities.This magnet, which is the most pow-erful magnet in China, was built atIHEP by the laboratory’s researchstaff. In addition, BES-III contains alarge array of 6,240 crystals ofCesium Iodide that are used to mea-sure the energies of the high-energygamma rays that are produced in thecollisions. The combination of thesuperconducting magnet and the large

crystal array enables the BES-IIIdetector to measure the energies andvelocities of the produced particleswith more than ten times better preci-sion than was previously possible withBES-II. To handle the huge data ratesexpected in the BES-III detector, aspecialized state-of-the-art high-speeddata communication system has beendeveloped and implemented.

BEPC-II’s double ring system wascompleted in October 2006, beamswere first stored during the followingmonth and first collisions were pro-duced in March 2007. The assemblyof the BES-III detector was completedin January of this year, and it wasmoved into the interaction region inearly April (see Figure 1).

In last weekend’s initial test run, apair of charmed particles, where onecontains a c-quark and the other ac-quark, was recorded in the detector

approximately every ten minutes. Adisplay of one of the first such eventsis shown in Figure 2. The collisionrate in the initial test run was about afactor of 4,000 times slower that theproject’s ultimate design goal of 6 or 7charmed-particle pairs per second.This lower rate was partly because theresearchers purposely limited theintensity of the electron and positronbeams in order to avoid possible dam-age to the very sensitive detection sen-sors of the BES-III spectrometer whilethey made sure that everything isworking as expected. The next day,intensities were increased and a ten-times higher collision rate was mea-sured. Over the next several weeks theintensity of the beams will graduallybe further increased while at the sametime BES-III’s nearly 20,000 detec-tion elements will be carefullyadjusted and calibrated. When thisprocess is completed, sometime in theearly Fall, the BES-III research pro-gram will begin.

Recently, researchers working atIHEP and at laboratories in Japan andthe United States have observed anumber of interesting and unexpectedproperties of charmed particles thatwill be investigated with unique sensi-tivity with BES-III; these observationshave added substantially to the world-wide particle physics community’sinterest in the BES-III research pro-gram. These new developmentsinclude the surprising observation thatneutral charmed mesons, that is,mesons containing a c-quark and ananti-up quark (u-quark), spontane-ously transform into anti-charmedmesons (i.e., u- and c-quark mesons)and vice versa, a phenomenon thatwas quite unexpected. BES-III will beuniquely able to perform importantmeasurements that categorize this pro-cess to help theoretical physicists

Figure 2. The first charmed-meson pair event seen in BES-III.

news and views


understand the root cause for thesetransformations. Recently, there havebeen hints that inside so-called Ds

mesons, which are particles comprisedof a c-quark and an anti-strange quark(s-quark), the constituent c- ands-quarks annihilate each other at a ratethat seems to be higher than that pre-dicted by theory. If this discrepancycould be unequivocally established,which is something that BES-III isparticularly well suited to do, thiswould be striking evidence for awhole new regime of forces and asso-

ciated particles in nature. In addition,the BES-II experiment at IHEP and anumber of experiments at other labo-ratories have uncovered a new class ofparticles that do not fit into the con-ventional quark model scheme. Todate, in spite of considerable effort,theorists have been unable to achievea compelling picture that describesthese states. More detailed measure-ments are necessary, and this is some-thing that BES-III will do.

It is estimated that these and themany other topics to be investigated

by BES-III correspond to an approxi-mately ten-year-long program ofintensive research. This research willbe carried out by an international teamof researchers from China, HongKong, Germany, Japan, Russia, andthe United States. The observation offirst collisions in the BEPC-II/BES-IIIfacility was an important milestone inthis research program.

ULRICH WIEDNER

Bochum

Path for Mass Mapping of Superheavies is Open It happened that just on August 8,

2008 (on the distinguished day of08.08.08!) the SHIPTRAP collabora-tion at GSI succeeded in directly mea-suring the masses of three nobeliumisotopes. Never before have mass val-ues of any isotope of the trans-ura-nium, or even trans-fermium elementsof the Periodic Table been directlydetermined. Since the idea of theexistence of an island of superheavynuclides was put forward about fortyyears ago, heroic attempts have beenundertaken to reach this alluring sitein the sea of nuclear instability. Step-by-step discoveries of new superheavyelements, performed over the lastdecades at GSI (Darmstadt) and atJINR (Dubna), paved the way towardthis mysterious island. Being landed,we still do not know too much on itsextension on the chart of the nuclides.

The masses, that is, the total bind-ing energies, allow us to explore thelandscape of the predicted island and toshed light on the structure and the sta-bilizing shell effects of superheaviesproviding information complementary

to nuclear decay spectroscopy investi-gations that are feasible in this region.

As the isotopes of new elementshave been identified by their a-decay,it was previously thought that about adozenlong a-chains, which originatefrom superheavy nuclides and end inthe region of well-known masses, canhelp to determine, although indi-rectly, the mass values of superheav-ies. However, the attempts tocomplete this goal by searching forsome unknown a-emitters in the longchains were unsuccessful so farbecause of very small a-decay proba-bilities. Thus, direct mass measure-ments of superheavies became theonly, but challenging, option left.

About ten years ago, H.-JürgenKluge came up with the idea to installa Penning trap system behind thevelocity filter SHIP at GSI in order toenable this kind of direct measure-ment for rare isotopes produced infusion-evaporation reactions at SHIP,utilizing the intense primary beamprovided by the heavy-ion accelera-tor UNILAC.

Penning traps are nowadays power-ful tools for mass measurements ofexotic short-lived nuclides. The mainPenning trap techniques used at theSHIPTRAP-facility are very similar tothose pioneered by ISOLTRAP atISOLDE/CERN. SHIPTRAP, however,utilizes exotic radionuclides fromheavy-ion fusion reactions after in-flight separation at SHIP, which arestopped in a gas cell, then extracted,cooled, and bunched with subsequent

Figure 1. Time-of-flight cyclotronresonance for doubly charged 253No-ions.

news and views


injection into a double Penning-trapsystem. After the isobar selection in thefirst trap, the mass of a charged particleis determined from its cyclotronfrequency, which is measured by atime-of-flight ion-cyclotron resonancetechnique. With this method one candetermine the mass value precisely. Theaccuracy of Penning trap mass spec-trometers achievable for radioisotopes,which is typically about 10−8 (corre-sponding to 1keV in the region ofA≈100) is superior to all other meth-ods. A great advantage of SHIPTRAPis its exceptional capability to measuredirectly the masses of trans-uraniumnuclides toward superheavies.

During the last experimental runin August 2008 the masses of threenobelium isotopes (Z = 102) withmass numbers A = 252, 253, and 254were measured at SHIPTRAP. Atime-of-flight resonance curve for253No is shown in Figure 1. It allowsdetermining the so far unknown mass

value for this nuclide on a level of afew times 10−8 accuracy.

The position of the measured nobe-lium isotopes in the a-decay chains isshown in Figure 2. As can be seen fromthis figure the mass values up to 269Dsand 270Ds (Z=110) are linked via alpha-chains and can now be connected to thedirectly determined nobelium mass val-ues. Notable information about the struc-ture of superheavies can be derived frommasses of different nobelium isotopes,which have a neutron number around thesemi-magic N=152. Just this number ofneutrons luckily constitutes the nuclide254No whose total binding energy wasmeasured directly at the SHIPTRAP.

As a consequence of this pioneeringexperiment the door for a mass mappingin the region of superheavy elements isopen. At present, nuclides with produc-tion cross-sections on the level of 500nbarn are accessible for direct massmeasurements with SHIPTRAP. Withplanned improvements of the system

this limit will be pushed further down: Itis planned to install a cryogenic gas-stopping cell and to introduce a non-destructive detection technique where amass value can be obtained using onlyone single ion for a mass determination.

This activity is underway in collab-oration with groups from GSI, Max-Planck Institute for Nuclear Physics inHeidelberg, from different universitiessuch as University of Mainz, München,and Giessen, as well as from the St.Petersburg Nuclear Physics Institute.

Figure 2. Alpha-decay chains starting from darmstadtium isotopes and passingthe directly mass-measured nobelium nuclides.

MICHAEL BLOCK

GSI, Darmstadt

YURI NOVIKOV

PNPI, St. Petersburg

news and views


IBA-Europhysics Prize 2009 for Applied Nuclear Science and Nuclear Methods in Medicine Call for Nominations

The Nuclear Physics Board of theEPS calls for nominations of the 2009IBA-Europhysics prize. The award willbe made to one or several individuals foroutstanding contributions to AppliedNuclear Science and Nuclear Methodsand Nuclear Researches in Medicine.

The Board would welcome pro-posals that represent the breadth andstrength of Applied Nuclear Scienceand Nuclear Methods in Medicine inEurope.

Nominations should be accompa-nied by a completed nomination form,a brief curriculum vitae of the nomi-nee(s), and a list of major publications.Letters of support from authorities inthe field that outline the importance ofthe work would also be helpful.

Nominations will be treated inconfidence and although they will beacknowledged there will be no furthercommunication. Nominations shouldbe sent to:

Selection Committee IBA Prize,Chairman Prof. G. Viesti,

Dipartimento di Fisica,, GalileoGalilei,“ Università di Padova,

Via Marzolo 8, I-35131 Padova,Italy. Phone/Fax: +32 049-8277124.

E-mail: [email protected] or [email protected]

For nomination forms and moredetailed information see: the websiteof the Nuclear Physics Division, http:/

/ific.uv.es/epsnpb/ and the website ofEPS, www.eps.org (EPS Prizes, IBA-Europhysics Prize).

The deadline for the submission ofthe proposals is January 15, 2009.

Sponsored by Ion Beam Applica-tions, Belgium.

General Description The European Physical Society

(EPS), through its Nuclear PhysicsBoard (NPB), shall award a Prize toone or more researchers who havemade outstanding contributions toApplied Nuclear Science and NuclearMethods and Nuclear Researches inMedicine (investigation, aid to diag-nosis, and/or therapy).

Such contributions shall representthe breadth and strength of AppliedNuclear Science and Nuclear Methodsin Medicine in Europe.

Prize Rules

1. The Prize shall be awarded everytwo years.

2. The Prize shall consist of aDiploma of the EPS and a sum of5000 € (to be shared, in case ofmore than one laureate).

3. The money of the prize is providedby the Belgian Company IBA (IonBeam Applications).

4. The Prize shall be awarded to oneor more researchers.

5. The Prize shall be awarded withoutrestrictions of nationality, sex, race,or religion.

6. Only work that has been publishedin refereed journals can be consid-ered in the proposals for candi-dates to the prize.

7. The NPB shall request nominationsto the Prize from experts in NuclearScience and related fields who arenot members of the Board. Call fornomination will be published inEurophysics News, Nuclear PhysicsNews International, and at thehomepage of the IOP journal“Physics in Medicine and Biology.”

8. Self-nominations for the awardshall not be accepted.

9. Nominations shall be reviewed bya Prize Committee appointed bythe NPB. The Committee shallconsider each of the eligible nomi-nations and shall make recommen-dations to the NPB, taking alsointo account reports of refereeswho are not members of the Board.

10.The final recommendation of theNPB and a report shall be submit-ted for ratification to the ExecutiveCommittee of the EPS.

GIUSEPPE VIESTI

Padova, Italy

calendar


2009 January 12–16

Stellenbosch, South Africa. Lasers andAccelerators

http://academic.sun.ac.za/lasers&accelerators/

January 19–28Stellenbosch, South Africa. 20th Chris

Engelbrecht Summer School in Theoreti-cal Physics

http://academic.sun.ac.za/summerschool/2009.html

January 26–30 Bormio, Italy. XLVII International

Winter Meeting on Nuclear Physics http://panda.physik.uni-giessen.do:8080/

indics/conferenceDisplay.py?confId=7

March 16–20 Bochum, Germany. European Nuclear

Physics Conference http://www.epl.rub.de/EUNPC

March 21–24 Prague, Czech Republic. International

Conference on Compating in High Energyand Nuclear Physics CHEP’ 09

http://www.particle.cZ/conferences/chep2009/

March 29–April 4 Knoxville, Tennesse, USA. Quark

Matter 2009 http://www.phy.ornl.gov/QM09

March 30–April 1 Pisa, Italy. EURISOL Design Study

Town Meeting http://www.eurisol.org/site01/town_

meeting-t-202.html

April 24–May 1Erice, Sicily, Italy. Workshop on

Hadron Beam Therapy of Cancerhttp://erice2009.na.infn.it/

May 4–8Dubrovnik, Croatia, Nuclear Structure

and Dynamicshttp://www.phy.hr/~dubrovnik09/

May 4–8 Vienna, Austria. International Topical

Meetingon Nuclear Research Applica-tions and Utilization of Accelorators(AccApp’09)

http://www-pub.iaea.org/MTCD/Meetings/Announcements.asp?confId=173

May 13–16 Chateau de Cadarache, France International Workshop on Nuclear

Fission and Fission-Product Spectroscopy hhttp://www.fission2009.com/

June 2–5 Mackinac Island, Michigan, USA 3rd International Conference on

“Collective Motion in Nuclei underExtreme Conditions” (COMEX 3)

http://meetings.nscl.msu.edu/COMEX3/

June 15–17Bad Honnef, Germany. Precision

Experiments of Lowest Energies for Fun-damental Tasts and Constants

http://www.mpi-nd.mpg.de/blaum/events/heraeus09/

June 21–26 New London, NH, USA

Gordon Conference on Nuclear Chemistry(Nuclear Structure)

http://www.grc.org/programs.aspx?year=2009&program=nuchem

June 30–July 4Dubna, Russia. Nuclear Structure and

Related Topicshttp://theor.jinr.ru/~nsrt/2009/

September 27–October 3 Milos, Greece 8th European Research Conference on

“Electromagnetic Interactions with Nucle-ons and Nuclei” (EINN 2009)

http://www.iasa.gr/EINN_2009/

September 28–October 2Sochi, Russia International Sympo-

sium on Exotic Nuclei EXON 2009http://exon2009.jinr.ru/

November 29–December 4Napa, California, USA. 4th Asia-

Pacific Symposium on Radiochemistry(APSORC’09)

http://apsore2009.Berkeley.edu/

2010July 19–23

Heidelberg, Germany. Nuclei in theCosmos NIC XI

http://www./sw.uni-heidelberg.de/nic2010

More information available under: http://www.nupecc.org/calendar.html. . . and check also http://www.ect.itÞMEETINGS

nuclear physics news · nuclear physics news volume 18/no. 4 vol. 18, no. 4, 2008, nuclear physics...

Documents