radioactive ion beams at fair-nustar

EPJ manuscript No.(will be inserted by the editor)

Radioactive Ion Beams at FAIR-NuSTAR

Challenges and advantages of high-energy exotic beams

Thomas Nilsson1,a

Fundamental Fysik, Chalmers Tekniska Hgskola, Gothenburg, SwedenInstitut fur Kernphysik, Technische Universitat Darmstadt, Germany

Abstract. The future FAIR facility will open up an unprecedented range of ex-otic nuclear beams in the energy interval between 0 - 1.5 GeV/u produced by theSuper-FRS. The envisaged experimental programme with radioactive beams, be-ing prepared within the NuSTAR collaboration, will cover most aspects of contem-porary physics within nuclear structure, astrophysics and reactions. An overviewof this programme is given, with emphasis on high-energy reactions.

1 Introduction

The issues addressed within nuclear structure, astrophysics and reactions are of fundamentalimportance for our understanding of the subatomic world and numerous aspects of our universe.Unlike many other branches of science, there are not only a few, critical problems to be attackedbut rather a multitude of interconnected questions, each highly relevant in its own respect. Anon-comprehensive list of the questions hitherto only partially resolved could be:

– How are complex nuclei built from their basic constituents?What is the effective nucleon-nucleon interaction?How does QCD constrain its parameters?

– What are the limits for existence of nuclei?Where are the proton and neutron drip lines situated?Which new structures arise near or at the limits?

– How does the nuclear force depend on varying proton-to-neutron ratios?What is the isospin dependence of the spin-orbit force?How does shell structure change far away from stability?

– How to explain collective phenomena from individual motion?What are the phases, relevant degrees of freedom, and symmetries of the nuclear many-

body system?– Which are the nuclei relevant for astrophysical processes and what are their properties?

What is the origin of the heavy elements?

Radioactive ion beams (RIBs) covering a variety of nuclear species and energies as well asstate-of-the art instrumentation are indispensable tools in the endeavour of attacking the issuesabove, and several additional burning topics within subatomic physics. It is therefore naturalthat the conception and construction of new and upgraded facilities providing RIBs is a majorconcern for science worldwide. In particular, the in-flight fragmentation method (see e.g. [1])can provide energetic beams of exotic isotopes, regardless of chemical properties, at energieswell suited for nuclear reaction studies. It is the method of choice for RIB production at thefuture FAIR facility, to be constructed at the existing GSI in Darmstadt, Germany.

a e-mail: [email protected]

2 Will be inserted by the editor

Fig. 1. Schematic view of the FAIR facility layout.

2 FAIR - Facility for Antiproton and Ion Research

The FAIR facility aims at being a world-leading facility in a large part of contemporary sub-atomic physics research. Through a complex of linear accelerators, synchrotrons, fragment sep-arator and storage rings (see fig. 1), beams of unprecedented intensity and quality of heavyions, antiprotons and radioactive ions will be produced. The facility and all envisaged experi-ments are described in detail in [2]. This will allow advancing the scientific frontier concerningour understanding of hot nuclear matter (within the CBM project), the internal structure ofhadrons (PANDA) and the structure of nuclei all the way out to extreme isospin (NuSTAR).Furthermore, the access to the high electromagnetic fields by relativistic heavy ions (HEDge-HOB/WDM) and highly charged ions (SPARC) will open up completely new avenues for atomicphysics studies. A rich programme using slow antiprotons (FLAIR) is foreseen as well.

2.1 Rare-ion production with the Super-FRS

The existing FRS facility at GSI provides already today relativistic beams of exotic speciesthrough in-flight fragmentation of heavy ions. To be able to substantially improve the sec-ondary beam intensities, a two-fold development is necessary: Firstly to increase the primarybeam intensities by faster cycling and by using lower charge states (thus decreasing the space-charge effects that limit the maximally allowed number of ions per bunch) in the SIS100/300synchrotrons to be constructed. Secondly, by increasing the acceptance of the separator device,the Super-FRS. This is being achieved by substantially larger apertures of all ion-optical stagesof the separator compared to the FRS which necessitates the use of superconducting magnets.For the “hot” fission process where the fission fragments obtain a large transversal momen-tum, this increased acceptance is crucial in increasing the transmission of the exotic speciesthat are created. Since fission of relativistic uranium beams have proved to be an extremelyprolific source of short-lived radionuclides [3], fission fragments in general and 132 in particularis considered as the benchmark case. Compared to the existing facility a gain of 3-4 orders ofmagnitude in secondary beam intensities is expected for fission fragments.

The Super-FRS will be able to deliver the secondary beams to three main experimental areas,namely the low-energy, the high-energy and the ring branch, as shown in fig. 2. The three areas

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Fig. 2. The Super-FRS with pre- and main separator and the three branches.

have, as their names indicate, different focii on the beam properties which have to be handledby the SIS-100/300 in conjunction with the Super-FRS. The fixed-target type experiments inthe first two branches require that the ions are well distributed in time, mimicking a DC beam.This necessitates slow extraction of the primary beam from the synchrotron. On the contrary,injection into the ring branch requires an ion pulse that is highly focused in time. This is achievedby fast extraction of the primary beam, which however puts very high demands on dissipatingthe thermal power dumped into the production target of the Super-FRS. Furthermore, in thelow-energy branch, the ions are to be degraded in energy shortly before the experimental set-u.Due to the varying charge states following the energy degradation, no subsequent separationis possible which puts stringent demands on the ion-optical properties of the preceding massseparation. The high-energy branch with its high-resolution separator is on the contrary inmany respects a continuation of the Super-FRS as an ion-optical device.

2.2 Experiments at the Low-energy branch

As indicated by its name, the Low-energy branch collects experiments making use of ion beamsat a lower energy than as produced in the Super-FRS. This encompasses several energy domains;stopped beams, energetic beams (3-150 MeV/u), and stopped and re-accelerated beams (0-60keV). The directly stopped beams constitute the domain of the DESPEC experiment, concen-trating on decay spectroscopy of the most exotic species to be produced using the Super-FRS.Decay studies frequently offer the very first information concerning very exotic isotopes on thefeasibility limit of production. The DESPEC set-up is consisting of several detection systemsoptimised for gamma ray, charged particle and neutron detection. The energetic beams willmake in-beam studies with highest resolution feasible, being the aim of the HISPEC set-up.HISPEC has as its main detection system the AGATA [4,5] advanced gamma-ray tracking array.AGATA represents the absolute state-of-the-art in gamma-ray detection technology and willalso be used at other existing and future leading European research facilities like e.g. SPIRAL-2[6]. The low-energy branch with the HISPEC and DESPEC experimental set-ups is depictedin fig. 3.

By stopping the radioactive ions in a gas volume, extracting and reaccelerating them usingelectrostatic devices, it is possible to convert the high-energy beam with large emittance toa low-energy and low-emittance beam of radioisotopes. This gives the opportunity to employthe wealth of experimental methods already developed since decades at ISOL-facilities like e.g.


Fig. 3. Schematic view of the low-energy branch showing the HISPEC and DESPEC set-ups. Forexperiments with MATS and LaSPEC, a gas-filled stopping cell takes the place of the DESPEC set-up.

ISOLDE [7] at CERN but without the obstacles frequently posed by the intricate chemistry ofthe production target and ion source systems at such facilities. These low-energy beams willbe exploited by the experiments LaSPEC and MATS, concentrating on laser spectroscopy andhigh-precision mass Penning-trap measurements, respectively, in order to investigate ground-state properties of exotic nuclear species. The well-established collinear and resonant ionisationmethods to be used within the LaSPEC project will permit precision measurements of dipoleand quadrupole moments, as well as charge radii far from stability. MATS is expected to yieldhighest attainable precision in measuring masses of unstable nuclei, down to a relative massuncertainty of ∆m/m ∼ 10−9. Furthermore, trap-assisted decay spectroscopy will be possiblewhere precision studies of decay properties can be performed without the influence of havingimplanted the decaying nuclei in a catcher material.

2.3 The High-energy branch

The high-energy branch at the Super-FRS will house only one experiment, the R3B (Reactionswith Relativistic Radioactive Beams) set-up. The R3B set-up is a generic fixed-target deviceoptimised for RIBs as they are produced from the Super-FRS, i.e. in the energy range of 0.3- 1.5 GeV/u. It is based on the existing ALADIN-LAND experiment [8] which has been usedfor inverse-kinematics reaction studies with RIBs since 1992, starting with the first completekinematics experiments on halo nuclei [9] and now extended to a large range of exotic systems[10], even beyond the drip-lines [11–13]. The R3B project aims at upgrading all existing detec-tor systems to the best available, as well as adding substantial new developments. A schematicpicture is shown in figure 4, indicating the various detector systems to be used for neutrons,charged particles, ions and gamma rays. Ion-by-ion tracking is employed to achieve character-isation of each event and thus a “cooling” of the RIBs from the Super-FRS. Separation andspectrometry of protons and ions are made by a superconducting dipole magnet with largeaperture, permitting neutrons to be detected simultaneously at forward angles. Through thekinematical focusing at relativistic energies, the detector systems approach a 4π coverage inthe centre-of-mass system, permitting kinematically complete experiments. In a later stage, ahigh-resolution spectrometer will be added to achieve optimum momentum resolution of therecoiling ions.


Fig. 4. Schematic view of the R3B set-up

Fig. 5. The complex of storage rings connected to the Super-FRS with the experiments ILIMA, EXL,ELISe and AIC.

2.4 The Ring branch

The ring branch allows injecting the rare isotopes from the Super-FRS into the complex ofstorage rings to be constructed at FAIR, as shown in fig. 5. RIBs at 740 MeV/u will be collectedand cooled through stochastic and electron cooling and subsequently be transferred to theexperimental storage ring NESR. The CR and NESR are themselves experimental devicesfor mass measurements within the ILIMA project. The methods of Schottky and isochronousmass measurements are adapted to high precision and shortest half-lives respectively, thuscomplementing the MATS project. Mass measurements of short-lived nuclei in a storage ringhave already shown their potential through experiments at the existing ESR at GSI [14].

The NESR will be the venue of three further experiments, using cooled beams. Light-ioninduced reactions using a gas-jet target will be performed within the EXL experiment, whereprecision measurement will be attainable through the cooled rare-isotope beam. Here, e.g.(in)elastic scattering, charge-exchange and, through the possibility of decelerating the storedbeam, transfer reactions will be feasible also at very low momentum transfer due to the thintarget. The loss in luminosity from the small target thickness can largely be regained by recir-culating the beam. The low-momentum transfer region carries the majority of the structuralinformation, however, the inverse kinematics infers that the recoiling particles have low ener-


Fig. 6. The ELISe electron spectrometer situated in the RIB-electron interaction zone. A horizontalpre-deflector is followed by a vertical momentum-analysing stage.

gies and the recoil detector set-up must be able to cover a considerable dynamic range. For theprojectile-like fragments, the subsequent dipole stages can serve as a spectrometer in conjunc-tion with suitable ion detectors. This applies as well to the other ring experiments investigatingnuclear reactions as indicated in fig. 5.

In the ELISe experiment, the well-proved precision method of electron scattering will forthe first time be used for studying short-lived nuclei. This is being achieved by combiningthe stored RIBs in the NESR with electrons in a small intersecting storage ring, in collidergeometry. This geometry requires a very specific electron spectrometer, where the electrons arefirst horizontally pre-deflected and subsequently momentum analysed in a vertically bendingdipole magnet as shown in fig. 6. The obvious experiment here is elastic electron scattering tomap out charge radii of exotic isotopes, but also inelastic scattering, electrofission and quasi-freescattering (e,e’X) can be addressed with pure leptonic probes.

The ELISe electron ring will in a later stage also serve in the AIC (Antiproton-Ion Collider)as storage ring for antiprotons, which will be produced in large amounts for the HESR andFLAIR programmes. The cross-section for annihilation of nucleons in nucleus-antiproton colli-sions depends strongly on the matter distribution, thus the difference in matter radii betweenneutrons and protons in exotic systems A

ZXN can be determined simply by counting the number

of A−1

Z−1XN and A−1

Z XN−1 nuclei created respectively.

All reaction experiments situated in the NESR storage ring extend certain aspects of scien-tific scope compared to the fixed-target experiments R3B and HISPEC through their additionalobservables and increased precision. However, due to the time needed for beam cooling whichis in the order of a few seconds, the most short-lived nuclei will remain the domain of thelatter class of experiments. We thus have a true complementarity between fixed-target and ringexperiments.


Table 1. Reaction types with high-energy beams measurable with R3B and corresponding achievableinformation. Many of the reactions also apply to EXL, ELISe and HISPEC.

Reaction type Physics goal

Knockout Shell structure, valence-nucleon wave function,many-particle decay channels, unbound states,nuclear resonances beyond the drip lines

Quasi-free scattering Single-particle spectral functions, shell-occupationprobabilities, nucleon-nucleon correlations, cluster structures

Total-absorption measurements Nuclear matter radii, halo and skin structuresElastic p scattering Nuclear matter densities, halo and skin structuresHeavy-ion induced Low-lying transition strength, single-particle structure,electromagnetic excitation astrophysical S factor, soft coherent modes,

low-lying resonances in the continuum,giant dipole (quadrupole) strength

Charge-exchange reactions Gamow-Teller strength, soft excitation modes,spin-dipole resonance, neutron skin thickness

Fission Shell structure, dynamical propertiesSpallation Reaction mechanism, astrophysics, applications:

nuclear-waste transmutation, neutron spallation sourcesProjectile fragmentation Equation-of-state, thermal instabilities,and multifragmentation structural phenomena in excited nuclei,

γ-spectroscopy of exotic nuclei

3 Nuclear reactions at FAIR-NuSTAR

Nuclear reactions are a crucial tool in all aspects of the proposed physics of the NuSTARcollaboration. The reaction classes that are attainable within the FAIR-NuSTAR projects arenumerous, and several of them are world-unique to the facility. The high-resolution spectroscopyplanned with HISPEC will open up excellent possibilities for reaction studies using single-step Coulomb excitation and fragmentation reactions, reaching even further from stability byusing secondary fragmentation of the RIBs. At lower energies, inelastic scattering, transferreactions and fusion evaporation reactions will be performed. By combining the HISPEC andDESPEC set-ups, Recoil Decay Tagging (RDT) can be used to unambiguously identify theresidual nucleus by its decay properties. Thus, it is possible to further suppress backgroundand pinpoint the reaction channel of interest.

However, from a European perspective, it is the high-energy reaction studies with RIBsat the high-energy and the ring branches that will be unique to FAIR-NuSTAR, also aftercompletion of the EURISOL facility [15]. The high beam energies encountered at the R3B andthe ring projects have several advantages but obviously also some drawbacks. One importantadvantage is the nature of the reaction mechanisms themselves; the combination of high energiesand heavy targets gives rise to Coulomb fields that can induce dissociation of the incomingnucleus. Here, the virtual photon reach high energies that can induce (γ, n) and (γ, p) reactionsas first-order processes. These can thus be used to study the astrophysically important inverseprocesses. In fragmentation reactions, the nucleons can largely be treated as independent entitiesin a Glauber approach [16]. Furthermore, the nuclear transparency of knocked-out nucleonsor clusters of nucleons is at a maximum which facilitates disentangling structure propertiesfrom effects of the reaction mechanism. Experimentally, the strong kinematical focusing ofrelativistic reaction products facilitates good coverage in the centre-of-mass system, but isinherently detrimental to the resolution which has to be met by excellent time and positionresolution. The width of the reaction programme at R3B is demonstrated in table 1, many ofthese reaction types apply to EXL and ELISe as well.


3.1 A workhorse revisited - quasi-free hadronic scattering

We will here go somewhat more into detail into one of the reactions to be exploited at FAIR-NuSTAR; the process of quasi-free scattering (QFS) as a direct method to study single-particleproperties in exotic nuclei. It is also closely related to knock-out reactions, which already con-stitute an established method for radioactive beams [17], albeit at lower beam energies. The useof quasi-free scattering as a spectroscopic tool has a long history within experimental nuclearphysics. From the 1960’s and onwards, the combination of synchrocyclotrons, capable of deliv-ering proton beams of several hundreds of MeV, coupled to spectrometer devices opened upthe possibility to study the evolution of shell structure of deeply-bound states through (p,2p)-reactions [18,19]. Later, the pure leptonic probe of quasi-elastic electron scattering has yieldeda substantial amount of additional information concerning valence and inner shell orbitals instable nuclei.

The quasi-free reaction mimics the elastic scattering process in several respects, beingof the type (x, xN), i.e. an incoming particle knocks out a nucleon or a cluster of nucleonslargely unperturbed by the surrounding nucleons. Looking at the kinematics involved in e.g.a AX(p, 2p)A−1Y -reaction in the laboratory system in classical kinematics, we have from mo-mentum conservation that:

kA−1 = k0 − k1 − k2 = −k3 (1)

where k1, k2 and k0 are the momenta of the scattered protons and the incident proton,respectively, and k3 is the momentum of the particle in the target nucleus being knocked out.The separation energy of the knocked-out nucleon is expressed as :

Es = T1 + T2 + TA−1 − T0 (2)

where T0, T1 and T2 are the kinetic energies of the incident proton and the scattered protons,respectively, and TA−1 is the kinetic energy of the final nuclear system of A-1 nucleons. We canof course eliminate all variables connected with the recoil of the residual nucleus so that weexperimentally only have to consider measuring the four-momenta of the two outgoing protonsto be able to deduce Es.

The quasi-free scattering process is an idealised picture building on the impulse approxima-tion [20], i.e. the momentum transfer to the knocked-out nucleon is sufficiently large so that theinteractions of the incoming and the scattered nucleons with its environment can be neglected.Thus, the gross features of nucleon-nucleon elastic scattering do remain unchanged. This isevident in the Distorted Wave Impulse Approximation (DWIA) theoretical framework [21,22]where the differential cross section for a reaction A(a, a′b)B can be factorised as:

d5σ

dΩa′dΩbdEa′

= SbFk(dσ

dΩ)a−b

∑

Λ

∣

∣T ΛL

∣

∣

2

(3)

where Sb is the spectroscopic factor of b, Fk is a kinematical factor,(dσ/dΩ)a−b is the two-

body cross section for a−b scattering and∑

Λ

∣

∣T ΛL

∣

∣

2

is the distorted momentum distribution forb inside the target nucleus A. Further explanation can be found in [23]. Thus, the spectroscopicinformation of the hole state obtained in the process can readily be obtained. An early exampleis shown in fig. 7. The factorisation of eq. (3) has been shown to be valid [24], also for protonenergies well below the energies encountered at R3B [23]. However, the presence of rescattering(i.e. multi-step) effects constitutes an important problem in interpreting data from quasi-freescattering experiments and can obscure the spectroscopic information from deeply bound states[25]. This is traditionally dealt with by limiting the studied region to kinematical conditionswhere the direct process is maximised, i.e. under similar conditions as in the elastic scattering.

In addition to the (p,2p) reaction, the knocked-out entity might be a neutron or cluster ofnucleons. (p,pn) reactions are excellent tools to probe neutron-hole states and test the impulseapproximation, but detection of the knocked-out neutron is experimentally harder than theproton counterpart [26]. Spectroscopic factors for clusters in light nuclei have as well beenextracted [21,27,28].


Fig. 7. An early example taken from [18] of a missing-energy spectrum showing the low-lying statesin 16O. The insets to the right show the angular dependency of the scattered protons in the symmetriccase.

The (p,2p) cross-section is strongly sensitive to the polarisation of the scattered nucleonwhich gives an angular momentum dependency. This has been thoroughly exploited using po-larised proton beams [29], where the analysing power yields information on the structure ofhole states.

3.1.1 QFS using radioactive beams

There is an evident interest to apply the power of quasi-free scattering also to nuclei far fromstability, but the limited intensity of the radioactive beams have so far restrained the methodto relatively light nuclei, e.g. the investigations of the cluster structure in 6,8He [28] done byChulkov et al1.

Taking the QFS reactions to radioactive nuclei introduces further complications; an obviousone being the necessity of working in inverse kinematics for investigations of all nuclei that areto short-lived or scarce to make up a reaction target. For proton-induced reactions, the protonbeam must be replaced with a hydrogen(-rich) target, and in the case of a liquid target with anextended thickness, a thorough reaction vertex reconstruction must be undertaken. In the caseof (p,2p) reactions in classical geometry, the protons are emitted with ∼ 90 with respect to eachother2, a reflection of the similarities to elastic scattering. This situation remains unchangedwhen going to inverse kinematics due to its quasi-free nature (whether the spectator nucleonsmove with the beam or sit in the target is in zeroth order equivalent), so we have to detectthe two outgoing protons with maximum efficiency in an angular range as close as possible toθ = 0− 90 with respect to the beam axis. A further obstacle is the many orders of magnitudeweaker beam current that is expected for most radioactive species, necessitating very gooddetection efficiency and also taking reaction events that are outside a coplanar geometry (allreaction products lie in a plane) into account. Here, the issue of rescattering can be expectedto be an obstacle in achieving quantitative spectroscopic information. However, the inversekinematics offers the unique advantage of making spectroscopy of the remaining nucleus thatwill continue in the forward direction. In a kinematically complete set-up, the reaction can befully characterised, thus one is able not only to tag the desired reaction but also to excludeevents where a large momentum transfer to the remaining system has taken place, i.e. theimpulse approximation is no longer fulfilled. This yields excellent opportunities to suppress therescattering background and could even be of interest for studying stable nuclei.

An attempt has recently been made to investigate the information content within the phasespace of non-optimised reaction kinematics. The THREEDEE code [30] was used [31] for thesimple system of (p,2p)-reactions with 400 MeV protons on 12C. Knock-out of protons from

1 After the school, a very comprehensive investigation of 9−16C by (p,2p) reactionswas presented by T. Kobayashi at INPC2007, Tokyo. The presentation is available underhttp://inpc2007.riken.jp/G/G1-kobayashi.pdf

2 This holds for the lower energy range of (p,2p) experiments, with increasing energy the relativistickinematics cause a focusing of the two protons in the beam direction.


Fig. 8. Drawings of the envisaged calorimeter CALIFA to be used with R3B for gamma rays andcharged particles. The left part of the figure also shows the outline of the micro-vertex silicon trackerdevice.

the 1s1/2 and 1p3/2 was considered with geometries deviating from optimum and the bindingenergy of the two states were artificially made equal to specifically explore the sensitivity to thel-value. A few results are displayed in figure 9, the upper left inset shows a coplanar geometrywith equal opening angle between the two protons and the incoming beam, θ1 = θ2. Thedifferential cross-section clearly increases when the kinematical conditions approach the freeproton-proton scattering. However, the sensitivity to the orbital of origin is evident. In thelower panels, the opening angle of both protons is kept fixed at θ = 45 (left panel) and = 30

(right panel) respectively, and the energy of one of the outgoing protons at 200 MeV. Thehistograms show the differential cross-section when varying the out-of-plane tilt angle β (seeupper right inset for clarification). The distributions corresponding to θ1 = θ2 = 45 show asizable cross-section and a clear sensitivity to the orbitals depopulated in the reaction, showingthat a considerable angular bite can be used to extract spectroscopic information. However,when simulating protons emitted at θ1 = θ2 = 30, the cross-section decreases rapidly andthe spectroscopic sensitivity largely disappears. Nevertheless, it seems feasible to extend theregions classically investigated in QFS in stable nuclei, which will be needed in order to workwith weak radioactive beams. Anyhow, this must be carefully investigated and bench-markedusing well-known cases of stable nuclei in inverse kinematics [32]. Such experiments are plannedat GSI in the near future.

At R3B, the experimental set-up is foreseen for this kind of reactions; a liquid hydrogentarget has already been operated at the existing ALADIN-LAND set-up at GSI and this will inthe forthcoming experiments be surrounded by a two-layer silicon micro-vertex tracker. For R3Ba high-resolution calorimeter for gamma rays and charged particles is foreseen. This will then actas a final layer for the scattered charged particles and allow a reconstruction of the four-momentaof the outgoing protons, deuterons or alpha particles. The outline of the calorimeter and trackergeometry is shown in figure 8. Furthermore, as depicted in fig. 4, neutrons, projectile-like ionsand protons can be detected to achieve complete kinematics and an exclusive characterisationof the reaction. The experimental possibilities do thus not only include (p,2p) reactions butalso e.g. (p,pn), (p,pα) and (p,pd). The latter could constitute a probe of T = 1 pairing alongthe N = Z line.

Through the future prospect of employing a polarised hydrogen target, the possibility ofperforming polarised quasi-free scattering in inverse kinematics would open up also for exoticnuclei. An interesting possibility is to study the evolution of spin-orbit properties along isotopicchains. However, this experimental programme will require extensive technical developments,furthermore, the decreased quasi-free cross-section will need the highest intensities possiblefrom the Super-FRS.


[deg]θ10 15 20 25 30 35 40 45 50 55 60

)]2

) [m

b/(

MeV

sr

2Ω

d 1Ω

/(d

E d

σ3 d

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

1/21s

3/21p

= 200 MeVp2 = Ep1

, E2θ = 1θ

[deg]β0 5 10 15 20 25 30

)]2

) [m

b/(

MeV

sr

2Ω

d 1Ω

/(d

E d

σ3 d

0

0.02

0.04

0.06

0.08

0.1

1/21s

3/21p

= 200 MeVp1

= 45 deg, E2θ = 1θ

[deg]β0 5 10 15 20 25 30

)]2

) [m

b/(

MeV

sr

2Ω

d 1Ω

/(d

E d

σ3 d

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

1/21s

3/21p

= 200 MeVp1

= 30 deg, E2θ = 1θ

Fig. 9. THREEDEE [30]calculation [31] of (p,2p)-reactions with 400 MeV protons on 12C. The his-tograms correspond to protons knocked out of an 1s1/2 (shaded) and 1p3/2 state respectively. See textfor further explanation.

Quasi-free electron scattering is as well a subject of the ELISe project, using (e, e′X) re-actions. Here, the capabilities of R3B and ELISe will complement each other excellently; e.g.systematic surveys of isotopic chains at the former versus high-precision studies of selectedcases at the latter.

3.1.2 Theory needs for future QFS experiments

The interpretation of QFS data has been the subject of thorough theoretical efforts in thepast, but the know-how has rapidly to be transmitted to new generations of reaction phe-nomenologists. Finding the domains of reliable spectroscopic observables when extending theinvestigations to non-optimised kinematical conditions will require a careful theoretical treat-ment. There is even an urgent need for realistic event generators based on solid underlyingphysics, to enable experimentalists simulating and optimising future experimental set-ups forQFS. These questions constitute a challenge for any young theorist in the field.

4 Summary

The NuSTAR programme will revive the full field of nuclear reactions through the extensionto very exotic, short-lived nuclear species. The high energies becoming available for reactionstudies open up a large range of reaction classes and permits either direct beam cooling instorage rings or indirect through high-resolution tracking of the secondary beams. The necessary


complication of working in inverse kinematics does also entail advantages since detailed analysisof the remaining nucleus becomes feasible, which could become interesting for studies of long-lived or even stable nuclei. Theory of nuclear reactions is a field that needs to be further revivedand developed with the huge efforts done for stable-beam physics as a starting point. This iscrucial in order to match the envisaged experimental efforts using radioactive beams at FAIRand elsewhere.

The author is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from theKnut and Alice Wallenberg Foundation. He is indebted to his co-spokespersons within the QFS@GSIproject, R. Lemmon and O. Kiselev, as well as G. Schrieder, L.V. Chulkov, T. Aumann, P. Egelhof, H.Simon, B. Jonson and C. Forssen for substantial input and fruitful discussions. This work was supportedby the Swedish Research Council and the German BMBF under Contract No. 06 DA 115.

References

1. Geissel H., Munzenberg G., Riisager K. Annu. Rev. Nucl. Part. Sci. 45, (1995) 1632. Gutbrod H.H., Augustin I., Eickhoff H., Groß K.D., Henning W.F., Kramer D., Walter G. (Eds.).

FAIR Baseline Technical Report. GSI, 2006. URL http://www.gsi.de/fair/reports/btr.html

3. Bernas M., et al. Nucl. Phys. A725, (2003) 2134. Bazzacco D., et al. AGATA. Tech. rep., GSI, Darmstadt, 2001. URL

http://www-win.gsi.de/agata/Publications/Agata pub-proposal.pdf

5. Simpson J. Jour. Phys. Conf. Ser. 41, (2006) 726. Lewitowicz M. these proceedings7. Kugler E. Hyp. Int. 129, (2000) 238. Blaich T., et al. Nucl. Instr. Meth. A314, (1992) 1369. Humbert F., et al. Phys. Lett. B347, (1995) 198

10. Aumann T. Euro. Phys. Jour. A 26, (2005) 44111. Simon H., et al. Nucl. Phys. A 791, (2007) 26712. Meister M., et al. Phys. Rev. Lett. 91, (2003) 16250413. Zinser M., et al. Nucl. Phys. A619, (1997) 15114. Radon T., et al. Nucl. Phys. A677, (2000) 7515. Cornell J. (Ed.). The EURISOL Report. GANIL, 2003. URL

http://www.ganil.fr/eurisol/Final Report.html

16. Glauber R. Phys. Rev. 99, (1955) 151517. Hansen P.G., Tostevin J.A. Annu. Rev. Nucl. Part. Sci. 53, (2003) 21918. Jacob G., Maris T.A.J. Rev. Mod. Phys. 38, (1966) 12119. Jacob G., Maris T.A.J. Rev. Mod. Phys. 45, (1973) 620. Serber R. Phys. Rev. 72, (1947) 100821. Chant N.S., Roos P.G. Phys. Rev. C 15, (1977) 5722. Chant N.S., Roos P.G. Phys. Rev. C 27, (1983) 106023. Samanta C., Chant N.S., Roos P.G., Nadasen A., Wesick J., Cowley A.A. Phys. Rev. C 34, (1986)

161024. Roos P.G., et al. Phys. Rev. Lett. 40, (1978) 143925. Cowley A.A., et al. Phys. Rev. C 57, (1998) 318526. Ahmad M., Watson J.W., Devins D.W., Flanders B.S., Friesel D.L., Chant N.S., Roos P.O., Wastell

J. Nucl. Phys. A 424, (1984) 9227. Yoshimura T., et al. Nucl. Phys. A 641, (1998) 328. Chulkov L.V., et al. Nucl. Phys. A 759, (2005) 4329. Kitching P., Miller C.A., Hutcheon D.A., James A.N., McDonald W.J., Cameron J.M., Olsen W.C.,

Roy G. Phys. Rev. Lett. 37, (1976) 160030. Chant N.S. Computer code THREEDEE. Univ. of Maryland (unpublished)31. Thompson I.J., Al-Khalili J.S. private communication32. The R3B and EXL Collaborations. Letter of Intent - Quasifree Hadronic Scattering Studies of

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