Electron-IonColliderDetectorRequirementsand

R&DHandbook

Version1.2February25,2020

Authors

ElkeAschenauer,AlexanderKiselev,RichardPetti,ThomasUllrich,CraigWoodyBrookhavenNationalLaboratory,NY,US

TanjaHorn,

TheCatholicUniversityofAmerica,WashingtonDC,US

YuliaFurletova,JeffersonNationalLaboratory,VA,US

PawelNadel-Turonski

StonyBrookUniversity,NY,US

LauraGonella,PeterJonesUniversityofBirmingham,UK

YordankaIlieva

UniversityofSouthCarolina,SC,US

KondoGnanvoUniversityofVirginia,VA,US

2

EditorsNotesThishandbookisacommunityeffort.Manycolleagueshavemadesubstantialandvaluablecontributions to this document and the studies it is based on.We consider this a livingdocumentthat,aswehope,getsfrequentlyupdatedandthusstaysrelevantforthosethatworkontherealizationofanEIC.EICUserGroupmembersandthoseinvolvedintheEICdetectorR&Dprogramsareinvitedtocontributetothisdocument.Ifyouwanttocontrib-utepleasesendtext(MSWord)andplots(preferablyinepsformat).AlexanderKiselevThomasUllrichAcknowledgementsTheauthorsare indebtedtothefollowingcolleaguesforcriticalandcrucialcontributionandinputinthepreparationofthisreport:M.Alfred,L.Allison,B.Azmoun,F.Barbosa,M.Boer,T.Cao,M.Chiu,I.J.Choi,E.Cisbani,M.Contalbrigo,A.Deldotto,S.DallaTorre,M.Demarteau,A.Denisov,J.M.Durham,A.Durum,R.Dzhygadlo,C.Gleason,M.Grosse-Perdekamp,M.Hattawy,X.He,H.vanHecke,J.Huang,C.Hyde,G.Kalicy,B.Kim,E.Kistenev,M.Liu,J.McKisson,I.Mostafanezhad,K.Park,K.Pe-ters,R.Pisani,W.Roh,M.Sarsour,C.Schwarz,J.Schwiening,C.L.daSilva,A.Sukhanov,X.Sun,S.Syed,R.Towell,G.Varner,R.Wagner,C.P.Wong,J.Xie,Z.W.Zhao,C.Zorn.

3

TableofContents1 INTRODUCTION..........................................................................................................................................5

2 MACHINEPARAMETERS..........................................................................................................................7 2.1 BEAMENERGIES,LUMINOSITIES...........................................................................................................................7 2.2 RATESANDMULTIPLICITY.....................................................................................................................................7 2.3 INTERACTIONREGION.............................................................................................................................................9

3 DETECTORPERFORMANCEREQUIREMENTS................................................................................12 3.1 PHYSICSCONSIDERATIONSFORDETECTORDESIGN......................................................................................12 3.1.1 KinematicsOverview......................................................................................................................................13 3.1.2 ScatteredElectrons.........................................................................................................................................14 3.1.3 Hadrons................................................................................................................................................................21 3.1.4 TheExtremeForwardRegion:RomanPots.........................................................................................22

3.2 DETECTORGOALS.................................................................................................................................................24 4 TECHNOLOGIESANDR&DNEEDS.....................................................................................................27 4.1 TRACKINGSYSTEMS..............................................................................................................................................27 4.1.1 CentralTracking...............................................................................................................................................27 4.1.2 ForwardsandBackwardsTracking.........................................................................................................33 4.1.3 RomanPots.........................................................................................................................................................34 4.1.4 Low-𝑄2Tagger.................................................................................................................................................37

4.2 CALORIMETRY........................................................................................................................................................38 4.2.1 ElectromagneticCalorimeters....................................................................................................................38 4.2.2 HadronCalorimeters......................................................................................................................................42 4.2.3 ZeroDegreeCalorimeter...............................................................................................................................43

4.3 PARTICLEID..........................................................................................................................................................43 4.3.1 HadronPID.........................................................................................................................................................43 4.3.2 Electronidentification...................................................................................................................................44 4.3.3 Detectortechnologies.....................................................................................................................................45

4.4 LUMINOSITYMEASUREMENTS...........................................................................................................................51 4.5 TRIGGERANDDATAACQUISITION.....................................................................................................................52 4.6 POLARIZATIONMEASUREMENTS.......................................................................................................................52 4.6.1 ElectronBeam...................................................................................................................................................52 4.6.2 ProtonBeam.......................................................................................................................................................53 4.6.3 LightIonBeams................................................................................................................................................53

5 THEEICR&DPROGRAM.......................................................................................................................53

REFERENCES......................................................................................................................................................55

4

5

1 IntroductionThe2015LongRangePlanforNuclearScienceintheUSrecommendsahigh-energyhigh-luminositypolarizedEICasthehighestpriorityfornewfacilityconstructionfollowingthecompletionofFRIB.TheEICwill,forthefirsttime,preciselyimagegluonsinnucleonsandnuclei.Itwilldefinitivelyrevealtheoriginofthenucleonspinandwillexploreanewquan-tumchromodynamics(QCD)frontierofultra-densegluonfields,withthepotentialtodis-coveranewformofgluonmatterpredictedtobecommontoallnuclei.ThissciencewillbemadepossiblebytheEIC’suniquecapabilitiesforcollisionsofpolarizedelectronswithpo-larizedprotons,polarizedlightions,andheavynucleiathighluminosity.InlinewiththisrecommendationtheLRPalsoemphasizedthatanEICwillrequiretoolsand techniques that are state-of-the-art or beyond and therefore recommends vigorousdetectorandacceleratorR&DinsupportoftheEIC.ThephysicsgoalsoftheEICwillprofitfromadvancesindetectortechnologytooptimizethephysicsoutcomeoftheexperiment(s).Improvementsincludereducingsystematicstothe lowest possible level in order to take advantage of the full luminosity for precisionmeasurementsandproviding thebestpossibleefficiencies andkinematic coverage.Thisdocument outlines the detector requirements and discusses the need for detector R&Dthatwillallowustomeetthesedemands.ItaimsatdescribingthedetectorR&Denvisagedforthetimelyconstructionofadetectorwiththerequiredperformanceandtopointoutareaswhereeffortsaremissingorareinadequatelycovered.Currently, R&D is conducted within a generic EIC detector R&D program supportedthroughfundsprovidedtoBNLbytheDOEOfficeofNuclearPhysics.ItisnotintendedtobespecifictoanyproposedEICsiteandisopentoallsegmentsoftheEICcommunity.Be-lowwewillalsogiveabriefsummaryoftheprogramandoftheeffortspursued.AlthoughhugeeffortswereandarebeingmadeindetectordevelopmentfortheLHCpro-gram,withmanybenefitstodetectortechnology,thereareneverthelesssignificantdiffer-encestothedemandsofanEICprogram.TheprincipalchallengesattheLHCarerelatedtothehigheventrateandespeciallythehighradiationlevelsassociatedwiththeppenergiesand luminosities required to address thephysics goals.Bothof theseproblemsaredra-matically reduced at an EIC. The primary new requirements are (i) an unprecedentedhermeticity to access the full 𝑥,𝑄!range and (ii) excellent tracking resolution and PIDcoverage over awide range ofmomenta to achieve the highest precision. The latter re-quires,amongotherthings,averylowmaterialbudgetbetweentheinteractionpointandthecalorimeters.ThesechallengesrequireR&DnowtoachievetheperformancegoalsandtoprepareforanoptimalphysicsprogramattheEIC.Thisdocument is structuredas follows: InSection2webrieflysummarize themachineparameters and emphasize the importanceof the InteractionRegion (IR)design and itsimpact ondetector integration anddesign. Section3 discusses the overall detector per-formancerequirementsdrivenbythephysicsprogram.IninSection4wereviewtheactu-alR&DneedsforthevariousdetectorcomponentsandinSection5wegiveabriefover-

6

viewoftheongoingEICR&Dprogram.HerewedotakeintoaccountthedifferentdetectordesignsunderconsiderationanddiscussthesimilaritiesanddifferencesonR&Drequire-ments.

7

2 MachineParametersThemachineparameterswerefirstdiscussedandlargelydefinedatthe10-weekINTpro-graminFallof2010[1].AlreadyatthatpointtwosubstantialfocusedeffortsatdevelopingadesignforanEICwereunderway,oneatBNL(eRHIC)andoneatJLAB(JLEIC).Becausebothoptionsaredrivenbythesamescienceobjectives,thetwoU.S.EICdesigneffortshavesimilarcharacteristics.TheparameterswereonlyslightlyrefinedfortheEICWhitePaper[2]thatwascompiledinpreparationfortheNSA2015LongRangePlanprocess.HerewegivetheperformancerequirementsandparametersaslistedintheWhitePaper(version2).Note thatdueto funding limitationsandconstructionscosts, theseparametersmightnotbereachedatthebeginningofEICoperationsbutonlyafteraseriesofupgradesinalaterstageoftheprogram.Nevertheless,anydetectordesignshouldbeabletocopewiththedemandsof thephysics-drivenrequirements.Whiletheenergyof thespecificbeamsdrivesthedemandsonthekinematiccoveragefortrackingandPID,theanticipatedlayoutoftheIRmakesintegrationofthedetectorintotheacceleratoraparticularchallengeforanydesign.2.1 BeamEnergies,LuminositiesTheEICmachinedesignparametersare:

• Highlypolarized(~70%)electronandnucleonbeams• Ionbeamsfromdeuterontotheheaviestnuclei(uraniumorlead)• Variablecenterofmassenergiesfrom√𝑠 ≈20to100GeV,upgradableto~140GeV• HighcollisionluminosityofL~1033-34cm-2s-1• Possibilitiesofhavingmorethanoneinteractionregion

Notethatforheavyionsthecenter-of-massenergieshavetobemultipliedby(𝑍/𝐴oftherespectiveions.ForAuionsthisfactoris~0.63.Theluminosityscalesingoodapproxima-tionwith 1/A, although inmost cases the quoted luminosity is given as per nucleon inwhichcasetheepandeAvaluesareidentical.TheimplicationsonthedetectorrequirementsaredetailedinSection3.2.2 RatesandMultiplicityForthedesiredenergyrangeTable1liststhereferringtotalepcross-sections.Thecross-sectionswerecalculatedusingPythia6andshouldberegardedonlyasanapproximationorballparkfigures.Itisinterestingtocomparethesecross-sectionswiththetotalinelasticppcross-sectionatRHICof~42mbat√𝑠=200GeVandthatattheLHCof~69mbat√𝑠=7TeV. In theEICrange thePythiacross-sectioncanbeapproximatedby thesimple func-

8

tion:𝜎"#"(𝜇𝑏) = 0.42+3.45log!𝑠,where𝑠 is the squareof the center-of-massenergy (inGeV2)thatiswellapproximated1by𝑠 = 4𝐸$𝐸%.

σtot(μb) Ee(GeV) 5 10 15 20Ep(GeV) 50 31.4 38.0 42.1 45.3100 38.0 45.3 49.8 53.0150 42.2 49.8 54.1 57.8200 45.2 52.9 57.9 61.4250 47.8 55.5 60.6 64.4

Table1:Totalepcross-sectionasafunctionofelectronandprotonbeamenergies.

Fromthecross-sectiononecaneasilyestimatetheapproximatedatarateatanEIC.ForL=1033 cm-2 s-1 =1000Hz/μbanda cross-sectionof50μb the total interaction rate is amoderate50kHz.Figure1depictstheparticleproductionratesasafunctionofpseudo-rapidityfor15GeVon250GeVepcollisionsataluminosityofL=1033cm-2s-1.EventsweresimulatedusingPythia6.Nocuts,forexampleonevent𝑄!orparticlemomentum,wereapplied."Charged"particlestermreferstoelectrons,positrons,andchargedpionsandkaons,while"neutrals"referstophotons,neutronsand𝐾&'.

Figure1:Particleproductionratesasafunctionofpseudo-rapidityfor15GeVon250GeVepcolli-sionsandaluminosityof1033cm-2s-1.Left:Meannumbersofparticlesperevent(leftaxis)andparti-cles per second per unit (η, φ) (right axis). Right: Particles per second per unit (θ, φ) i.e. the η -dependentfluxatadistanceof1mfromtheinteractionpoint.Bendinginthesolenoidfieldisnotac-countedwhenbuildingtheseplots.

Overalltheinteractionrateaswellasthemultiplicity/occupancyinanEICdetectorisra-thersmall,especiallywhencomparedwithRHICorLHCconditions.

1Inmostkinematiccalculationinthisdocumentthemassesofelectronandprotonarene-glectedthussubstantiallysimplifyinganykinematiccalculations.

dN/(d

e�dq

dt)dN

/(dd�dq dt)

dN/dd�p

er e

vent

d d

9

2.3 InteractionRegionTheIRdesignandproper interfacingofmachinecomponents inthedetector installationarea to the sub-detector systems,whichare close to thebeam line(s) isof aparamountimportance for thesuccessof theEICphysicsprogram. Ingeneral, the ideal IRdesign isachievedwhentheacceleratorisabletoprovidehighluminositycollisioneventswithmin-imalspreadofthebeamkinematicparametersandadverseeffectontherestofthephysicsdetectorsisminimal.Thisinparticularimpliesthatmachineelementsdonotobscurethecriticallyimportantpartsoftheacceptance,providinginparticularaclearpathtotheaux-iliarydetectorsinstalledtenthofmetersawayfromtheInteractionPoint(IP).Wherein-terferencewiththescatteredtrackscannotbeavoided,theadverseeffectsshouldbeataminimum.Machine-relatedbackgroundsshouldbereducedtothelowestlevelpossible.Requirements and constraints, related to the IR design, come from various sources dis-cussedthroughout thisdocument.Theycanbeconventionallybrokendown into the fol-lowingcategories:BeamparametersattheIP:Reachinghighestpossibleluminosityingeneralrequiresbringingthefirstfocusingquadsascloseaspossible totheIP.This impliestheuseof thestrongfocusingoptics.Bothre-quirementsareinobviousconflictwiththephysicsmeasurement.Theformeroneinevita-blyobscuresforwardandbackwardacceptanceoncethebeamlineelementsare“insert-ed”intotheregionprimarilyallocatedforthemaindetector.Thisharmstheregistrationofthelow𝑄!scatteredelectronsanddiffractiveprotons,respectively.Thelatterrequire-mentcausesunwanted(proton)beamdivergenceattheinteractionvertex,whichatalev-elofseveralhundredmicro-radiansnegativelyaffectsthe𝑝( reconstructionofdiffractivescatteredprotonsand,assimulationsshow,undermines thequalityof the imagingdata.Hadronbunchelongationbeyondfewcentimeterswouldcausesevereinefficiencyinthevertex reconstruction procedure and in the scattered track parameter determination ingeneral,asthereactionproductsstarttomissafractionofthevertexdetectorlayers.Vacuumchamberandbeampipes:Severaldetailsof thevacuumsystemdesignat the IParepotentially inconflictwith therequirements imposedbyphysicsmeasurements.Thebeampipearound the interactionvertexcannotbemadeinfinitelythin(itispresentlyassumedtobe1mmthickBeryllium),andatthesametimeitcannothavetoosmallaradiussincethesynchrotronfanproducedby the incomingelectronbeamdue to thebending in theupstreamquadsneeds topassthrough it unobstructed. This fact alonehas obvious implications for vertex reconstruc-tion,especiallyforlow-momentumparticles.Beampipesectionscanbeconnectedtoeachothereitherbywelding(whichadverselyaffectsthemaintenanceworkincasebeampipeneedstoberemoved)orusingrelativelythickflanges,whichcanobscuretheacceptanceofthephysicsdetector.Thereismostlikelynospaceforthevacuumpumpsinthedetectorinstallation region of the beam pipes, therefore most likely the NEG coating should be

10

used.However,thiscoatingneedstobeactivatedfromtimetotime,whichprocedureim-pliesbeampipeheatingbyupto200degreeCelsius.Itdoesnotlookfeasibletodisassem-blethevacuumsystemeverytimeforthistypeofmaintenancework.Therefore,heatingelementsaswellastheproperinsulationrequiredtoprotectthesensitiveneighboringde-tectors(likesiliconvertextracker)mustbemostlikelyintegratedintothebeampipede-sign.This,however,againincreasesboththematerialbudgetandtheeffectivebeampiperadius.Hadron-goingdirection:It is assumed that thevacuumchamberand thevacuumpipedesignat the IPprovideaclearacceptanceconeof±4mradfortheneutronsafternuclearbreak-up,seeFigure14.Modellingofdiffractiveprocessesshowsthatatthehighestconsideredprotonbeamener-gy of~250GeV (eRHICdesign) one requires an unobstructed acceptance cone of up to±5mradwith respect to the outgoinghadronbeam linedirection for the close-to-beam-energyscatteredprotons, seeFigure13.This requirementextendsup to theanticipatedlocationof theRomanPotstations, seesection4.1.3.At lowerprotonbeamenergies (aswellasintheJLEICcaseingeneral),therequirementonthisangularacceptanceispropor-tionallyhigher,upto20mradorso.Thiscanbeachievedbyinstallingtrackingstationsinthe locationof the first (weak) largeacceptancedipolemagnet rightdownstreamof thecentral tracker in the hadron-going direction. Also a noticeably large momentum ac-ceptance for thechargedproductsof thenuclearbreak-up forawiderangeofmagneticrigiditiesisneeded.Electron-goingdirection:Thetwokeydetectorsthatneedtobeintegratedintothedesign,arethelow-𝑄! taggerandthe luminositymonitor.The formerdetector,whichwouldmost likely comprisea setofsmall-scale trackers and an electromagnetic calorimeter, needs to have sufficient ac-ceptance,unobstructedbythebeampipeandthesynchrotronphotonmasks.ItneedstobeintegratedwiththefirstbendingdipoledownstreamoftheIP.Thelatterone,whichwillverylikelybedesignedsimilartotheZEUSluminositymonitor,requiresanunobstructedpath for thebremsstrahlungphotons from the𝑒𝑝 → 𝑒𝑝𝛾 reactionbetween the incominghadronandtheoutgoingelectronbeamlines.Thisalso impliessufficientspaceto installthedipoleofthepairspectrometeraswellasthephotonand𝑒)𝑒*conversion-paircalo-rimeters.Machine-relatedbackgrounds:ThemajorbackgroundsdirectlyrelatedtotheIRdesignare(i) thesynchrotronfanpro-duced by the electron beamwhen it passes through the final focusing quads right up-streamofthecentraldetectorand(ii)theproductsofthebeam-gasinteraction,associatedwiththehadronbeam.The formeronerequirescarefuldesignof thebeampipesystem,withseveralmasksalongtheway.However,itcausestheunwantedbeampipewideningintheoutgoingelectrondirection.Thedownstreammaskscannotbeinstalledtooclosetothemaindetectorbecauseofthesynchrotron-photonback-scattering.Thelatteronecanproduceheavyhadronicbackgroundinthemaindetectorcorrelatedwiththebunchcross-ings, due to thehigh enoughproton-nucleus andnucleus-nucleus cross-sections, for theep- andeA-running, respectively.These twosourcesofbackgroundare somewhat inter-

11

connected,sincethebeampipeheatingduetothesynchrotronfancausesexcessiveout-gassingfromitswallmaterial,thusincreasingtherateofthebeam-gasinteractions.Otherauxiliarydetectorslikebeampositionmonitorsandthepolarimeters(fortheprotonandthelightionbeamsinparticular)mayalsoneedtobeinstalledclosetotheIPlocation.Thiswillrequireadditionalintegrationeffortsinthisalreadyverydenseenvironment.

12

3 DetectorPerformanceRequirements3.1 PhysicsConsiderationsforDetectorDesign

InthisdocumentweusethecoordinatesystemandthedirectionsofthebeamsasdefinedforHERAatDESY.Thehadronbeamgoesinthepositivezdirection(0o)andtheelectronbeaminthenegativez-direction(180o)asindicatedinFigure2.Particleswithapositive𝑝+havepositivevaluesinpseudo-rapidity,𝜂>0,particleswith𝑝+<0havenegativepseu-do-rapidityvalues.Theacceptancesofthevariousdetectorgroupsareonlymeantfor il-lustration.

Figure2:Illustrationofthereferenceframeusedinthisdocument

InordertodefinetherequirementforaEICdetectorallrelevantphysicsprocessesneedtobeconsidered.Inthemostgeneraltermstheyencompass:

• Inclusivemeasurements(ep/eA→e′+X),whichrequireeitherthedetectionofthescatteredleptonorthefullscatteredhadronicdebriswithhighprecision(Jacquet-Blondelmethod,seesidebar)inordertoextract𝑥,𝑄!,and𝑦.

o Physics:StructureFunctionssuchas𝑔,,𝐹!,𝐹&o General requirements:Verygoodscatteredelectron IDandexcellentener-

gy/momentumandangularresolutionofe’• Semi-inclusiveprocesses(ep/eA→e′+h+X)thatrequiredetectionincoincidence

with the scattered leptonof at leastone (currentor target fragmentation region)hadron,h.

o Physics:TMDs,HelicityPDFs,FFs(withflavorseparation),di-hadroncorre-lations,Kaonasymmetries,multiplicities,etc.

o Generalrequirements:ExcellenthadronID,i.e.,𝜋±,𝐾±,𝑝±separationoverawide momentum and rapidity range, full φ-coverage around 𝛾∗, wide 𝑝( coverage,excellentvertexresolutionforcharm,bottomseparation.

• Exclusiveprocesses,whichrequiredetectionofallparticlesinthereaction.

1

0.5

1.52.03.0 4.0 5.0

0

-1

-0.5

-1.5-2.0

-3.0-4.0-5.0

p/A

Barrel

z

e−

Electron Endcap Hadr

on

Endcap

Far-forward Electrons

Far-forward Hadrons

η

13

o Physics: DVCS, exclusive (diffractive) VM production for GPDs and partonimaginginbT.

o Generalrequirements:Largerapiditycoverage,highmomentumresolution,widecoverage in𝑡 = (𝑝/,123 − 𝑝/,45)!viaRomanPots,sufficientacceptancefor neutrons in ZDC to detect breakup of nucleus in eA and determina-tion/approximationofimpactparameterofeAcollision.

Jacquet-BlondelandMixedMethodsIngeneral,thekeykinematicvariables𝑥,𝑄!,andyarederivedfromthemomentumandangleofthescatteredelectronalone.However,atsmallscatteringanglestheresolutionfor the scattered lepton deteriorates. This problem is addressed by reconstructing thelepton kinematics purely from the hadronic final state using the Jacquet-Blondel [3]method or using amixedmethod like the double anglemethod [4],which uses infor-mation fromthescattered leptonandthehadronic finalstate.AtHERA, thesemethodsweresuccessfullyuseddownto𝑦of0.005.Themainreasonthishadronicmethodren-ders better resolution at low y follows from the equation𝑥67 = (𝐸 − 𝑝+9:;)/𝐸$ ,where𝐸 − 𝑝+9:; is thesumover theenergyminus the longitudinalmomentumofallhadronicfinal-stateparticlesand𝐸$ istheelectronbeamenergy.Thisquantityhasnodegradationof resolution for 𝑦 < 0.1 as compared to the electron method, where 𝑦67 = 1 −(1 − cos 𝜃$)𝐸$!/𝐸$ .Toallowforefficientunfoldingofmeasuredquantities,i.e.crosssec-tions and asymmetries, for smearing effects due to detector resolutions and radiativeeventsand retain the statisticalpower it is important tohavea survivalprobability ineachkinematicbinof~70%orbetter.3.1.1 KinematicsOverview

BeforegoingintodetailsitisinstructivetorecallthekinematicsofDISinthe𝑄!-𝑥planeforepcollisions.ShowninFigure3aretheisolinesofthescatteredelectronenergy,i.e.thelinesofconstantenergy,aswellas the isolinesofscatteredelectronpseudo-rapidity, i.e.linesofconstantη.Herewecanalreadynotethat low𝑥/low-𝑄!physics isrelatedtoex-tremely forwardgoingelectronsat large rapidities,while for large𝑥, large𝑄!processeswehavetodealwithbackscatteredelectrons.Figure4showsasimilarplotbutfortheiso-linesofthestruckquark.Inbothfiguresanarrowspacingofisolinesofavariableindicatesthatavariableisverysensitivetothekinematicsofthecollisionandhenceyieldsagoodintrinsicresolution.Thedirectionoftheisolinesdeterminestowhichkinematicparameterthevariableismostsensitive.Theactualresolutionisaconvolutionoftheintrinsicresolu-tionofthereconstructionmethodandtheexperimentalresolutionofthemeasuredquan-tities. From the isolines picture one can for example predict that the Jacquet-Blondelmethodyieldsapoor𝑄!determinationovernearly theentirephase-space.The intrinsicresolutionof𝑦67 ontheotherhandisquitegoodasthe𝐸< isolinesaredenseandmostlyparalleltotheyisolines.Theydeterminationfromtheelectronmethodatlowyisnearlyimpossiblebecausetheelectronenergyisnearlyconstantoveraverywideregionofphasespace. Conversely,we can exploit thewide spacing of𝐸$! isolines to define a sample of

14

events thathaveanearlyconstantscatteredelectronenergywithoutactuallymeasuringthisenergy.

Figure3:IsolinesofthescatteredelectronenergyEe’andηfor20GeVon250GeVepcollisions.

Figure4:IsolinesofthestruckquarkenergyEqandpseudorapidityηfor20GeVon250GeVepcolli-sions.

3.1.2 ScatteredElectrons

η = −5

η = −4

η = −3

η = −2

η = −1

η = 0

η = 1η = 2

E e′=

20 G

eV

Ee′=18 GeV

Ee′=2 GeV

Ee′=16 GeV...

Ee′=22 GeV

Ee′=40 GeVEe′=60 GeV

Ee′=180 GeV

Ee′=24 GeV

...

...

Isolines of scattered electron energy Ee′ Isolines of scattered electron pseudo-rapidity ηIsolines of constant inelasticity y

ep: 20 GeV on 250 GeV

x5−10 4−10 3−10 2−10 1−10 1

)2 (G

eV2 Q

2−10

1−10

1

10

210

310

410

510

y = 1

y = 0.1

y = 0.01

η = 6η = 5η = 4η = 3η = 2η = 1η = 0η = −1

η = −2

η = −3η = −4η = −5

E q=1 G

eVE q=

3 GeV

E q=5 G

eV… …

E q=18

GeV

E q=25

GeV

E q=45

GeV

E q=22

5 GeV

Isolines of struck quark energy Eq Isolines of struck quark pseudo-rapidity η

ep: 20 GeV on 250 GeV

x

)2 (G

eV2 Q

2−10

1−10

1

10

210

310

410

5105−10 4−10 3−10 2−10 1−10 1

15

Figure5below, illustratesthekinematicsof thescatteredelectronforvarious𝑄!ranges(integratedoverall𝑥),aswellasdifferingbeamenergycombinations.Thez-axes (colorscale)intheplotsreflectsthecross-section,thedistancefromthecenterpointdenotesthemomentumofthescatteredelectronandthedirectionsreflectstheactualoneintheinter-action.TheeventswereproducedwiththePythia6generator.

123456789

1011

p (GeV/c)

e

10 GeV on 100 GeV, Q2 > 0.1 GeV2

1

0.5

1.5

2.0

3.0 4.0 5.0

0

-1

-0.5

-1.5

-2.0

-3.0-4.0-5.0η

1

2

3

4

5

6p (GeV/c)

e

5 GeV on 100 GeV, 0.1 < Q2 < 1 GeV2

0

-1

-0.5

-1.5

-2.0

-3.0-4.0-5.0

η

0

1

2

3

4

5

6p (GeV/c)

e

5 GeV on 100 GeV, 50 < Q2 < 60 GeV2

00

1

0.5

1.5

2.0

3.0 4.0 5.0

0-0.5

η

123456789

101112

p (GeV/c)

e

10 GeV on 50 GeV, 0.1 < Q2 < 1 GeV2

-1

-0.5

-1.5

-2.0

-3.0-4.0-5.0

η

0123456789

101112

p (GeV/c)

e

10 GeV on 50 GeV, 50 < Q2 < 60 GeV2

00

1

0.5

1.5

2.0

0

-1

-0.5

-1.5

η

16

123456789

1011

p (GeV/c)

e

10 GeV on 100 GeV, 0.1 < Q2 < 1 GeV2

-1

-0.5

-1.5

-2.0

-3.0-4.0-5.0

η

123456789

1011

p (GeV/c)

e

10 GeV on 100 GeV, 1 < Q2 < 2 GeV2

-1

-0.5

-1.5

-2.0

-3.0-4.0

η

123456789

1011

p (GeV/c)

e

10 GeV on 100 GeV, 8 < Q2 < 10 GeV2

0.50

-1

-0.5

-1.5

-2.0

η

123456789

1011

p (GeV/c)

e

10 GeV on 100 GeV, 50 < Q2 < 60 GeV2

1

0.5

1.5

2.0

0

-1

-0.5

-1.5

η

123456789

101112

p (GeV/c)

e

10 GeV on 100 GeV, 100 < Q2 < 200 GeV2

1

0.5

1.5

2.0

3.0

0

-1

-0.5

η

0123456789

101112

p (GeV/c)

e

10 GeV on 100 GeV, Q2 > 200 GeV2

1

0.5

1.5

2.0

3.0

0-0.5

η

17

Figure 5: Kinematic of the scattered electron for various𝑄2bins as well as different beam energycombinations.Fordetailsseetext.

Afewthingsshouldbenoted.Atagivensetofbeamenergies,thelowerthe𝑄!themoreforward(negativeη)thescatteredelectrongoes.Onlyatthehighest𝑄!doesthescatteredelectronbackscatter(positiveη).Alsonoticethatastheelectronbeamenergygoesupthescatteredelectronismoreandmoreboostedtonegativeη.Anotherimportantobservationisthatthekinematicsoftheelectrondoesnotchangewhenvaryingthehadronbeamen-ergy.Thishasenormousconsequencesforthechoiceofbeamenergycombinations.Foradetectorthatisoptimizedforelectronmeasurementsinagivenrange,ingeneralitisoftenbettertovarythehadronbeamenergythantheelectronenergyifmeasurementsatadif-ferent√𝑠aredesired. However,forcertainsemi-inclusivemeasurementsitcouldbera-therdesirabletomaintainhadrons inthesimilarkinematicconditionsiftheseconditionsareoptimizedforthehadronPID.An alternative viewof showing the𝑄! − η relation is illustrated in Figure6 for protonbeamenergyof250GeVand10,15,and20GeVelectronbeamenergy.

Figure6:Scatteredelectron𝑄2,ηforvariouselectronbeamenergiesandfixedhadronbeamenergy.

2468

10121416182022

p (GeV/c)

e

20 GeV on 100 GeV, 0.1 < Q2 < 1 GeV2

-1

-1.5

-2.0

-3.0-4.0-5.0

η

2468

10121416182022

p (GeV/c)

e

20 GeV on 100 GeV, 50 < Q2 < 60 GeV2

1

0.50

-1

-0.5

-1.5

-2.0

η

10 GeV on 250 GeV 15 GeV on 250 GeV 20 GeV on 250 GeV

)2 (G

eV2

Q

-110

1

10

210

310

-5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 -5 -4 -3 -2 -1 0 1

18

Itisalsohelpfultolookatthekinematicsofthescatteredelectroninbinsofxand𝑄!.Fig-ure7showsthetypicalacceptanceofanEICinthe(𝑥,𝑄!)planeforeAcollisionsfor√s=90GeVand45GeV.TheblackboxesindicatetherangesofthefollowingplotsshowninFigure8.Note thatwith theexceptionofarea5(large𝑥and𝑄!), thescatteredelectrontravelsclosetothebeamline;inthelow𝑥region(areas1and2),whichisimportantforsatura-tionphysicsandDVCSitscattersatextremelysmallangle𝜂<-3.

Figure7:EICacceptanceforeAcollisionsinthex,𝑄2plane.Theblacksquaresindicatethekinematicrangesofthefiguresbelow(Figure8).

1

10

10-3

103

10-2

102

10-1 110-4

x

Q2 (G

eV2 )

0.1

EIC 3s = 90 GeV, 0.01 ) y

) 0.95

EIC 3s = 45 GeV, 0.01 ) y

) 0.95

Measurements with A � 56 (Fe): eA/ѥA DIS (E-139, E-665, EMC, NMC)� iA DIS (CCFR, CDHSW, CHORUS, NuTeV) DY (E772, E866)

perturbativenon-perturbative

g

c d

e

f

2468

1012141618202224

p (GeV/c)

e

20 GeV on 100 GeV, 0.1 < Q2 < 1 GeV2 , 3∙10-5 < x < 2∙10-4

-1

-1.5

-2.0

-3.0-4.0-5.0

η

!

02468

1012141618202224

p (GeV/c)

e

20 GeV on 100 GeV, 0.1 < Q2 < 1 GeV2 , 5∙10-4 < x < 3∙10-3

-3.0-4.0-5.0

η

!

19

Figure8:Kinematicofthescatteredelectronforthe𝑥and𝑄2rangesindicatedinFigure7.

For thedetectionof thescatteredelectronweconcludethat for𝑄!>1.0GeV2,arapiditycoverage-4<η<1issufficient,whilefor𝑄!<0.1GeV2adedicateddetectorsuchasalow-𝑄!taggerisrequired.SinceelectronIDmostcertainlydoesrequireelectromagneticcalorimetry(EMC)itisuse-fultolookattheDeepVirtualComptonScattering(DVCS)process,ep(A)→e′+p’(A’)+γ,wherethephotonmeasurementdoeslikewiserequireanEMC.Figure9showstheenergy-rapidity relationof thephoton.Note that increasing thehadronbeamenergyaffects themaximum photon energy at a fixed η. From these results we conclude that a pseudo-rapiditycoverage-4<η<1issufficienttocapturetheDVCSphoton.

2468

1012141618202224

p (GeV/c)

e

20 GeV on 100 GeV, 3 < Q2 < 20 GeV2 , 1∙10-3 < x < 8∙10-3

0

-1

-0.5

-1.5

-2.0

-3.0-4.0

η

!

2468

1012141618202224

p (GeV/c)

e

20 GeV on 100 GeV, 7 < Q2 < 70 GeV2 , 3∙10-2 < x < 1∙10-1

-1

-1.5

-2.0

-3.0

η

!

02468

1012141618202224

p (GeV/c)

e

20 GeV on 100 GeV, 200 < Q2 < 1000 GeV2 , 0.1 < x < 1

1

0.5

1.5

2.0

3.0

0

-1

-0.5

-1.5

η

!

20

Figure 9: Photon energy versus rapidity in DVCS processes for various hadron beam energies andfixedelectronbeamenergyof15GeV.Plotsarefor𝑄2>1GeV,0.01<y<0.85.

Figure10:Momentumdistributions for the scatteredelectrons (black),photons (orange),allnega-tivelychargedhadrons(red)fordifferentpseudo-rapiditybinsinthelaboratoryframeforbeamen-ergiesof15GeVon250GeV.AlsoshownarethedistributionsfornegativelychargedPions(blue),Ka-ons(green)andantiprotons(violet).Nokinematiccutshavebeenapplied.

-5-4-3-2-1012345

Energy (GeV)-110 1 10

Energy (GeV)-110 1 10

Energy (GeV)-110 1 10 210

15 GeV on 50 GeV 15 GeV on 100 GeV 15 GeV on 250 GeV

Entri

es

10

210

310

410

510

10

210

310

410

10

210

310

410

1

10

210

310

410

-110 1 10

Entri

es

1

10

210

310

410

510

-110 1 101

10

210

310

410

510

-110 1 101

10

210

310

410

510

-110 1 101

10

210

310

410

510

p (GeV/c) p (GeV/c)

p (GeV/c) p (GeV/c) p (GeV/c) p (GeV/c)

p (GeV/c)p (GeV/c)p (GeV/c)p (GeV/c)

-110 1 10 210

Entri

es

1

10

210

310

410

510

-110 1 10 210

Entr

ies

10

210

310

410

510

�����Ѡ�����

�����Ѡ�����

�����Ѡ�����

�����Ѡ�����

�����Ѡ���� ����Ѡ���� ����Ѡ����

����Ѡ����

����Ѡ���� ����Ѡ����

-110 1 10 -110 1 10 -110 1 10 -110 1 10

All 15 GeV on 250 GeV

/<

K<

p

e<

h<

a

21

3.1.3 HadronsWenowturntotherequirementforhadrons.Figure10showstherelativeyieldofchargedhadrons, and pions, kaons, and antiprotons in comparison to the scattered electron forvariouspseudo-rapiditybinsfor15GeVon250GeVepcollisions.Fortheentirepseudora-pidityrangeshownhere(-5<η<5)negativepions,kaonsandantiprotonsshowthesamemomentumdistributions,withnegativepionshavingafactor~3-5highermultiplicityasnegativekaonsandantiprotons. In thecentraldetectorregion(-1<η<1) themomentaareoftypically0.1GeV/cto4GeV/cwithamaximumofabout10GeV/c.Wearenowlookinginmoredetailintothehadronkinematicsusingchargedpionsasanexample.Figure11showstheηversus𝑝( andηversuszdistribution for threedifferentbeamenergycombinations:15GeVelectronbeamon50,100,and250GeVprotonbeam.Itturnsoutthatarangeof-4<𝜂<3.5coversalmosttheentirekinematicregionin𝑝( andzthatisimportantforphysics.

Figure11:Distributionofchargedpionsin𝑝𝑇andη(upperrow)andzandη(lowerrow).Distribu-tionsareforepcollisionswithfixedelectronbeamenergyof15GeVand50,100,and250GeVprotonbeamenergy.Thefollowingcutshavebeenapplied:𝑄2>1GeV2,0.01<y<0.95,p>1GeV.

Figure12showsthemomentumversuspseudo-rapiditydistributionforchargedpionsfordifferentcenter-of-massenergiesinep.Intheupperrowthehadronbeamenergyisfixedat250GeVandtheelectronbeamenergyisvariedfrom10to20GeV.Inthelowerrowthe

15 GeV on 50 GeV 15 GeV on 100 GeV 15 GeV on 250 GeV

-5-4-3-2-1012345

pT

-110 1 10pT

-110 1 10pT

-110 1 10

15 GeV on 50 GeV 15 GeV on 100 GeV 15 GeV on 250 GeV

-5-4-3-2-1012345

z0.60.40.20 0.8 1 0.60.40.20 0.8 1 0.60.40.20 0.8 1

z z

/(

22

electronbeamenergyisfixedat15GeVandtheprotonbeamenergyisvariedfrom50to250GeV.Twothingsshouldbenoted:(i)Whenincreasingtheelectronbeamenergythehadronsareboostedmoretonegativerapidity,while(ii)increasingthehadronbeamen-ergyinfluencesmostlythemaximumhadronenergyatafixedpseudo-rapidity.FromFigure12onecanconcludethatinthe-2<𝜂<3range𝜋/𝐾/𝑝separationbelow5GeV/cshouldbesufficient.However,atlargepositiverapiditiestherequirementsarera-therchallenging,demanding𝜋/𝐾/𝑝separationupto~50GeV/c.

Figure12:Distributionofchargedpionsinpandηfor6differentbeamenergies.Thefollowingcutshavebeenapplied:𝑄2>1GeV2,0.01<y<0.95,z>0.1.

3.1.4 TheExtremeForwardRegion:RomanPotsAttheendofthissectionwediscusstheneedforthedetectionofforward-goingscatteredprotons from exclusive reactions such as DVCS, as well as of decay neutrons from thebreakupofheavyionsinnon-diffractivereactions.Ingeneral,forexclusivereactions,onewishestomapthefour-momentumtransfer,𝑡,ofthehadronicsystem,andthenobtainanimagebyaFouriertransform,for𝑡closetoitskinematiclimituptoabout1.5GeV2.Oneofthemostchallengingconstraintsfortheinteractionregionanddetectordesignfromexclu-sivereactionsistheneedtodetectthefullhadronicfinalstate.

15 GeV on 50 GeV 15 GeV on 100 GeV 15 GeV on 250 GeV

-5-4-3-2-1012345

p (GeV/c)-110 1 10

p (GeV/c)-110 1 10

p (GeV/c)-110 1 10 210

10 GeV on 250 GeV 15 GeV on 250 GeV 20 GeV on 250 GeV

-5-4-3-2-1012345

p (GeV/c)-110 1 10

p (GeV/c)-110 1 10

p (GeV/c)-110 1 10 210

/(

23

Figure 13: The scattering angle vs. scattered protonmomentum in the laboratory frame forDVCSeventswithdifferentbeamenergycombinations.Thefollowingcutshavebeenapplied:1GeV2<𝑄2<100GeV2,0.01<y<0.85,10-5<x<0.5and0.01<t<1GeV2.Theangleoftherecoilinghadronicsys-temisdirectlyandinverselycorrelatedwiththeprotonenergy.Itthusdecreaseswithincreasingpro-tonenergy.

Figure13showsthecorrelationbetweenprotonscatteringangleindiffractiveepevents(e+p→e’+p’+X),anditsmomentum.Itillustratesthattheremainingbaryonicstatesgointheveryforwardiondirection.Evenattheprotonenergyof50GeV,theprotonscatteringanglesonlyrangetoabout25mrad.Atprotonenergiesof250GeV,thisnumberisreducedto 5mrad. In all cases, the scattering angles are small. Because of this, the detection oftheseprotonsisextremelydependentontheexactinteractionregiondesign.Atpresentitisanticipatedthattheprotonsscatteredinthe~5mradconearoundthehadronbeamdi-rectionshouldbedetectedbyaRomanPotsystemfewtenthsofmetersawayfromtheIP.Above~5mradasetoftrackingstationsinthelocationofthefirst(weak)bendingmagnetintheoutgoinghadrondirectionshouldbeused.OneofthebigchallengesinmeasuringdiffractiveeventsineAcollisionsis,apartfromde-tecting the rapidity gap itself, tobeable todistinguishbetween coherent (nucleus staysintact) and incoherent (nucleusdecays). Theonlypossiblewayensuringexclusivity forelectron-nucleuscollisionsforheavynucleiistovetothenuclearbreakup.Thisisrealizedby requiringnodecay-neutrons in thehadron-goingdirection.Howefficient this canbedone depends on the angular acceptance of a neutron-detecting device such as a Zero-DegreeCalorimeter(ZDC)aswellas theemittanceof thebeam.Figure14showsthere-sultsofsimulationusingthediffractiveeventgeneratorSartre[5]inconjunctionwiththenuclearbreakupgeneratorGemini++.Plotted is the inefficiency to tagan incoherentdif-fractiveeventasafunctionoftheangularacceptanceforneutrondetectionfor50GeVAuand100GeVAlbeams.Anormalizedemittance𝜀==0.2×10-6mandβ∗=5cmwereused.TheinefficiencylevelsoutandreachesaplateauwhenalldecayneutronsarecapturedintheacceptanceoftheZDC.Themagnitudeoftheplateauisduetothelackofneutronemis-sionatverylow𝑡(whereinfactitislessrelevantbecausethecoherenteventsdominate

proton momentum (GeV/c)

0 50 100 150 200 250

prot

on s

catte

ring

angl

e (m

rad)

0

5

10

15

20

25

30

1

10

210

310

41015 GeV on 50 GeV

15 GeV on 100 GeV

15 GeV on 250 GeV

24

thediffractive cross-section). The figure shows that thedesired angular acceptanceof aZDCshouldbearound±4mrad.

Figure14:InefficiencytodetectaneutronfromanuclearbreakupindiffractiveeAcollisionasafunc-tionoftheangularacceptanceofaneutrondetectingdevicesuchasaZero-Degree-Calorimeter(ZDC)for50GeVAuand100GeVAlbeams.Fordetailsseetext.

Studies[6]showedthatinSIDIS,collisiongeometriesineAcanbedeterminedbyutilizingtheZDCsincethenumberofforwardneutronsproducedanddetectedintheZDCissensi-tivetothepathlengthofthepartonandfragmentationofthecollidingnucleonalongthevirtualphotondirectioninthenucleus.Alsohere,aconsiderablylargeZDCacceptanceismandatory.Itisanticipatedatpresentthata~10interactionlengthssandwich-ZDCwithtransversesizeof~60x60cm2andinternalcompositionsimilartotheonedevelopedforSTARforwardupgrade[7]willbesufficient.3.2 DetectorGoalsIntheprevioussectionwelistedtherequirementsthatcanbederivedfromthekeyphys-icsmeasurementsatanEICintermsofrapiditycoverage,momentumreach,andelectron,photon,andhadronidentification.Whatevolvesisadetectorwiththefollowingkeyfea-tures:

• Hermeticcoverage,closeto4πacceptance(pseudo-rapidityrangeupto±4)• Lowmaterialbudgetonthelevelof3-5%of𝑋/𝑋'forthecentraltrackerre-

gion• Trackingmomentumresolutioninfew%range• ReliableelectronID• Goodπ/K/pseparationinforwarddirectionupto~50GeV/c• Highspatialresolutionofprimaryvertexonthelevelof<20microns

OtherrequirementscanbederivedfromexperiencesatHERAand,tosomedegree,fromLHCexperiments.Table2summarizesallrequirementsasa functionofpseudo-rapidity.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

1<10

1

2SHQLQJ�$QJOH�¨ѡ��PUDG�

Inefficiency

���*H9�$X�EHDP ����*H9�$O�EHDP

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

1<10

1

2SHQLQJ�$QJOH�¨ѡ��PUDG�

Inefficiency

pF/pEHDPʜ�����PUDGpF/pEHDPʜ���PUDG

25

Theyareessentially identical for JLEICandeRHICmachinedesigns. Howtheserequire-mentsaremetandwithwhatpotentialtechnologiesissubjectofthenextchapter.

26

Table2:PhysicsrequirementsforaanEICdetector

EIC

Det

ecto

r Req

uire

men

ts

ηN

omen

clat

ure

Trac

king

Elec

tron

sπ/

K/p

PID

HC

AL

Muo

ns

Res

olut

ion

Allo

wed

X/X

0Si

-Ver

tex

Res

olut

ion σ E

/EPI

Dp-

Ran

ge (G

eV/c

)Se

para

tion

Res

olut

ion σ E

/E

-6.9

— -5

.8

↓ p/

AAu

xilia

ry

Det

ecto

rs

low

-Q2 t

agge

rδθ

/θ <

1.5

%; 1

0-6 <

Q2

< 10

-2 G

eV2

…

-4.5

— -4

.0In

stru

men

tatio

n to

se

para

te c

harg

ed

parti

cles

from

pho

tons

2%/√

E

-4.0

— -3

.5

-3.5

— -3

.0

Cen

tral

Det

ecto

r

Back

war

ds D

etec

tors

σ p/p

~ 0

.1%×p

+2.0

%

~5%

or l

ess

TBD

π su

ppre

ssio

n up

to1:

104

≤ 7

GeV

/c

≥ 3σ

~50%

/√E

-3.0

— -2

.5

-2.5

— -2

.0

σ p/p

~ 0

.05%

×p+1

.0%

-2.0

— -1

.57%

/√E

-1.5

— -1

.0

-1.0

— -0

.5

Barre

lσ p

/p ~

0.0

5%×p

+0.5

%

σ xyz

~ 2

0 μm

, d 0

(z) ~

d0(rφ

) ~

20/p

T GeV

μm

+

5 μm

(10-

12)%

/√E

≤ 5

GeV

/cTB

DTB

D-0

.5 —

0.0

0.0

— 0

.5

0.5

— 1

.0

1.0

— 1

.5

Forw

ard

Det

ecto

rsσ p

/p ~

0.0

5%×p

+1.0

%

TBD

≤ 8

GeV

/c

~50%

/√E

1.5

— 2

.0

2.0

— 2

.5≤

20 G

eV/c

2.5

— 3

.0σ p

/p ~

0.1

%×p

+2.0

%3.

0 —

3.5

≤ 45

GeV

/c3.

5 —

4.0

↑eAu

xilia

ry

Det

ecto

rs

Inst

rum

enta

tion

to

sepa

rate

cha

rged

pa

rticl

es fr

om p

hoto

ns4.

0 —

4.5

… > 6

.2Pr

oton

Spe

ctro

met

erσ i

ntrin

sic(|t|)

/|t| <

1%

; Ac

cept

ance

: 0.2

< p

T <

1.2

GeV

/c

�1

27

4 TechnologiesandR&DNeedsThemajority of R&D in HEP andHENP is currently related to LHC phase-I (ALICE andLHCb)andphase-IIupgrades(ATLAS,CMS).Hereradiationhardnessandhigh-ratecapa-bilitiesare the topR&Dprioritiesespecially forppcollisions in thehigh-luminosityLHCera. Less emphasis is put on PID with the notable exceptions of the LHCb RICH (andTORCHupgrade)systems.SeveralR&Deffortsrelatedtophase-IsuchasMAPSSi-Sensors,RICHPID, andGEMbasedTPC readoutshavebynowconcluded since thedetectors arenowbeingconstructed.AsillustratedintheprevioussectionsmanyrequirementsforanEICareuniqueandthere-foredemandR&DthatisnotcoveredbythecurrentmainstreamHEPandHENPR&Def-forts.InthefollowingwediscussthepossibletechnologiesthatcouldbedeployedandtowhatextentR&DisnecessarytomakethesetechnologiesavailableforanEICdetector.4.1 TrackingSystems4.1.1 CentralTracking4.1.1.1 MainTrackerThetasksofthemaintrackerare(i)toallowforhighlyefficienttrackfindingofchargedparticles scattered at central rapidities, (ii) precise determination of particle kinematics(momentaandscatteringangles)and,totheextentparticulartechnologyallows,(iii)par-ticipationinleptonandhadronPIDaswellas(iv)providingroughtiminginformation(op-tionally). Unlike the LHC detectors the tracker should have very small overall materialbudget,on the levelofa few%of theradiation length. It should fulfil thebasic require-ments in terms of redundancy, in particular provide sufficient number of independentmeasurementspertrack(intheorderof fewtoseveraldozensofspacepointsasantici-patedpresently,althoughthedetailedtrackfindingefficiencystudieshavenotbeenper-formedyet).SincetheEICphysicscommunityclearlyexpressed its interest intwo inde-pendentgeneral-purposeEICdetectors, the trackingR&Dprogramshould identifymorethanone viable technology for themain tracker. For various reasons, depending on thechoiceofaparticulartechnology(longenoughleverarmfortrackfitting,efficientmultipletrackseparation,sufficientnumberofpointsfor𝑑𝐸/𝑑𝑥measurement),butalsobecauseofthelimitedspaceinsideanaffordable(orreadilyavailable)solenoidmagnet,atypicalsizeofthemaintrackerisdeterminedtobearound2minlengthandupto80cminouterra-dius.Theinnerradiusshouldbesufficienttoaccommodatethevertexdetector.Incaseofanall-siliconmaintrackerthevertexandthemaintrackerarecombined.Theoptionscon-sideredsofarare:

• (A) Medium size TPC: design either similar or identical to the sPHENIX centraltracker.Moderatespatialresolution,somewhatcompensatedbythelargenumberofindependentmeasurementpointsforeachtrack(sPHENIXdesignspecsare200-250μmperspacepointandupto40pointspertrack).IfneededonecanpossiblyimprovebothparameterssignificantlyforanEICapplication.ForexampleILCR&D

28

istargetedatobtainingbetterthan100μmresolutionperpointinthewholevol-ume, even foramuch largerTPC; alsoone canmost likelydouble thenumberofpad rows as long as the electronics costs are acceptable. Detector convenientlyprovides3Dpointsfortrackingwithnoambiguities,aswellasalimitedmomentumrangeparticleIDvia𝑑𝐸/𝑑𝑥measurement.Calibrationprocedurehowevermaybecumbersome,especiallyathigherluminositiesinthepresenceoflargespacechargedistortionsduetothehighionbackflow.Ionbackflowcanbereduceddrasticallybyaproperchoiceofgasmixtureandoperatingvoltage,but typicallyatacostofsignificantdeteriorationof the𝑑𝐸/𝑑𝑥 resolution.This typeofdetectorwill sufferfromapile-upeffectssincethe ionizationproducedbytracks fromseveralbunchcrossings issimultaneouslypresent inthegasvolume,duetothe limitedelectrondriftvelocity(ofanorderof30-80μm/ns,whichcanresultinatotaldrifttimefromthecentralmembranetothereadoutplaneofupto~30μs).Thismayormaynotadversely affect track finding and track-to-event association procedures in theeventreconstruction,giventherelativelylowchargedtrackmultiplicitiesoftypicalDISevents(ofanorderofonechargedtrackperunitofpseudo-rapidity).

• (B)Strawtubes:designsimilartothePANDAcentraltracker.Highenough1Dspa-

tialresolutionintheradial-to-wiredirection,typicallybetterthan150μmaveragedover the tubevolume,plaguedhoweverby the left-right ambiguity similar to thedriftchambers.Spatialresolutioninthedirectionalongthewirescanbeprovidedbymeasuringtimedifferenceofsignalsarrivingtobothendsandisingeneralra-therpoor, intheorderof~1cm.Detectorstacksofseverallayerscanbedesignedwithindividuallayersinstalledatsmallstereoanglestoeachother(fewdegrees),in order toprovide the coarse coordinatemeasurement along thebeam line alsofromtheskewedUV-coordinatesystem.Theadverseeffectinthiscaseissignificantgapsbetweenlayers(solowergeometricefficiency)duetothefactthatlayer“con-tainer volumes” are no longer cylindrical but rather hyperbolic once the stack isgluedtogether.Detectorcanbeusedwithatleast1barovertheatmosphericpres-sure(whichmeansbetter𝑑𝐸/𝑑𝑥duetothehigherionizationpertrackunitlength).Intheover-pressuremodethedetectorisself-supporting.Shortdriftlengthmeansthedetectorisingeneralfastandwithappropriateelectronicsonecanuseclustercountingtechniqueforimproved𝑑𝐸/𝑑𝑥measurement.

• (C) Drift chamber: design similar to the ZEUS central tracker. Depending on the

driftcelldesign(withthecellsingeneralorientedalongthebeamline)thedetectorcanhavebasictrackingpropertiessimilartothestrawtubetracker:decent1Dres-olutionandfastresponse,butpoorresolutionalongthewires,andleft-rightambi-guity.Operationalpropertiesofthedriftchambersolutionareofacertainconcern,sincedependingonthedesigndetailsonebrokenwiremaycauseshuttingdownofawholechambersegment.

• (D)All-silicondetector:thisoptionwouldbeacompactallsilicondetector,madeof

vertexandtrackingdetector(see4.1.1.2),maintrackerandforwardandbackwardtrackers(see4.1.2).Differentpartsofthedetectorwouldhavetobeoptimizeddif-

29

ferently.Themaintrackercouldbeequippedeitherwithpixelorstripdetectors.Incase of pixel detectors, amonolithic solution, such as theDMAPS technology de-scribed in4.1.1.2,wouldprovide smallerpixels and lowermaterial, andbemorecosteffectivethanhybridpixeldetectors.Atpresenttime,DMAPSandstripdetec-torscanprovidespatialresolutiondowntoafewµm,andtimeresolutionintheor-deroffewtensofns.ApotentiallyinterestingtechnologytomonitorforuseinanEICmaintrackerwouldbefasttimingdetectors.State-of-the-artdevelopmentsfortheATLASHGTDbasedonLGADsensorsanddedicatedreadoutASICcanachievetimeresolutionoftheorderoftensofps[8].Technicallythepicosecondleveltim-ingallowssuchdetectorstoprovide–atleastintheory–veryreasonablePIDforuptoafewGeV/cmomentumparticles,evenforveryshort,ofanorderof1m,flightpath.Atthemoment,howeverthesedetectorsfeatureapixelpitchintheorderofammandhavea largepowerconsumption(1.3mmand<300mW/cm2 for theAT-LASHGTD8),whichmakes themunsuitable foroperationatanEIC.Shoulddevel-opmentsinthistechnologyprogresstowardsreducingpixelsizeandoptimizetheelectronicsdesigntolowpowerconsumption,thiswouldbeaninterestingoptiontoaddPIDtoasiliconmaintracker.

• (E)Micromegas tracker: design similar to theCLAS12 tracker. Several concentric

micromegas cylinders composedof the “curved tile” buildingblocks cover all theradialspacebetween~20cmand~80cm.Suchadetectorcanprovidedecent1Dcoordinatemeasurementofanorderof~100μm inboth tangentialdirection (C-layer)andalongthebeamline(Z-layer).TheconfigurationwithstereolayersmustbepossibleaswellbutmoreR&Disrequiredtoprovethis.Thissolutionwillalsomost likelyprovide lessthan10pointspertrack.VigorousR&DisalsoneededtoexplorethedoublesideMPGDsoptionthatwoulddoublethenumberofpointspertrackataminimumcostformaterialbudget.It isanticipatedthatdetectoropera-tion in the so-calledmicro-driftmodemustbepossible.This couldprovide short“tracklet” seeds for the track finder rather than “single point” measurements aswell as improved𝑑𝐸/𝑑𝑥performance.Theperformanceofmicromegas inmicro-driftmodemaysufferfromthestrongsolenoidmagneticfield.

Dependingonthedetailsoftheparticulardesignthematerialbudgetofallthesesolutionscanbesufficientlysmall,wellbelow10%radiationlength.Thismaycomeatacostofper-formanceforoptions(B),(D)and(E),sinceingeneralboththetrackerresolutionandthematerialbudgetwillscalewiththenumberoflayers.Reducingthenumberoftrackinglay-ers is only possible up to the point when track finding efficiency will start degrading,whichisinparticulartrueforthemicromegasoptionandfortheall-silicontrackerincaseof1Dstripimplementation.Onecanseeminglyachievetherequiredperformancelevelintermsofmomentumresolu-tionwithanyof theoptionsabove,althoughthedetailedMonte-Carlostudieshavebeenperformedonlyfortheconfigurations(A),(D)and(E).

30

Aslow“volumetracker”likeaTPCcanbecomplementedattheinnerandtheouterradiusbyfewcylindricalMicroPatternGaseousDetector(MPGDs)layersoffast2Dtrackingde-viceswithspatialresolutionbetterthan100µm,whichwouldprovideseedtrackscorre-latedwiththebunchcrossingaswellasservethepurposeofTPCcalibration.Primecan-didate technology for this would be cylindrical micromegas (see above), but the moremodern µRWELL option may be considered as well. Similarly, cylindrical MPGD layers(micromegasorµRWELLdetector)attheinnerandtheouterradiuswiththeappropriatereadoutstripdesigncanbeaddedtoaStrawtubesorDriftchambertrackertoprovidethesub-millimeterpositionresolutioninthedirectionalongthebeamaxis.4.1.1.2 Vertex/SiliconTrackerAsiliconvertexandtrackingdetectorattheEIChastofulfilthreetasks:

• Determine the vertex with the high precision (in conjunction with the forward-backwardssilicontrackers).

• Allow the measurement of secondary vertices for heavy-flavor physics (e.g. F2,charm).

• Low-𝑝( tracking, extending the rangeof the central tracker to tracks that curluptoomuchtobedetectedinthemaintracker.

Tofulfilthesetasksrequiresasmallpixelsize(20x20µm2),andlowmaterialbudget.ThemostpromisingtechnologytosatisfytheserequirementsareMonolithicActivePixelSen-sors (MAPS). Current, state-of-the-artMAPS are theMIMOSA sensor used for the STARHFTatRHIC[9],andtheALPIDEsensordesignedfortheALICEITSupgrade[10].WhilsttheMIMOSAsensorisatraditionalMAPSdetectorbasedonchargecollectionbydiffusion,the ALPIDE sensor is the first of a new generation ofMAPS fabricated in a commercialCMOSimagingtechnologyonhighresistivityepitaxiallayer.Thistechnologyallowstode-pletepartofthesensorvolumewithareversebiasvoltageof-6V.Chargeisthusinpartcollectedbydrift.AcrosssectionofanALPIDEpixel illustratingtheprocess isshowninFigure15.Adepletionregiondevelopsaroundasmallcollectionelectrode.Electronicsishostedinseparatedp-wells.Thispixellayoutconfigurationprovidesasmalldetectorca-pacitance to ensure lownoise, fast readout, and lowpower consumption.Moreover, theavailability ofmultiplenestedwells offeredbyCMOS technologies allows theuseof fullCMOSelectronics,andthusthe integrationofmoreadvancedreadoutarchitectureswithrespecttothetraditionalMAPSrollingshutterreadoutusedbytheMIMOSAsensor.TheALPIDEchip,developedbya collaboration formedbyCCNU (Wuhan,China),CERN,INFN(Italy),andYonsei(SouthKorea),containsanovellow-powerin-pixeldiscriminatorcircuitthatdrivesanin-matrixasynchronousaddressencodercircuit,readoutbyanend-of-columnlosslessdatacompression.Thedigitizationofthesignalwithinthepixelelimi-natestheneedforananaloguecolumndriver,reducesthepowerconsumptionsignificant-lyandallowsforfastread-out.TheALPIDEchipfeaturesa4μsintegrationtime,apowerconsumptionof less than39mW/cm2,andan intrinsicspatialresolutionofbelow5μm.

31

WiththeALPIDEsensorandthefinalstaveandFPCBdesignusedintheITS,atotallayerthicknessesof~0.3𝑋/𝑋'canbereachedforrelativelyshortstaves(upto40cmorso,suf-ficientforatypicalEICdetectorbarrelvertextracker).

Figure15:SchematiccrosssectionofanALPIDEpixelintheTowerJazz180nmCMOSimagingtech-nologywithdeepp-wellallowingintegrationoffullCMOSlogic[10].

WithrespecttoALPIDE,theEICwouldcertainlybenefit in improvements inthe integra-tiontime2aswellasinafurtherreductionoftheenergyconsumptionandmaterialbudgetgoing towards0.1-0.2%radiation lengthper layer.Timing-wise theultimategoalof thistechnologywouldbetotimestampthebunchcrossingswheretheprimaryinteractionoc-curred.Thismayimposedifferentrequirementsdependingonthemachinedesign,butisingeneraldrivenbytheexpectedinteractionrateatthehighestluminosities.MorerecentdevelopmentsofMAPSsensorshavefocusedonachievingfulldepletionofthesensorvolumeinordertocollectchargebydrift.Chargecollectionthroughdriftresultsinfastersignals,lesschargespreadingatthecollectionelectrodeleadingtobettersignal-to-noise,andimprovedradiationhardnesswithrespecttocollectionbydiffusion.Whilstra-diationhardnessandfastchargecollectionaresignificantforexperimentsattheHL-LHC,thecapabilityofcollectinglargerchargeinsmallerpixelswouldbebeneficialtoimprovespatialresolutioninhighprecisionlepton-hadronandlepton-ioncolliders.AnumberofcommercialCMOStechnologiesprovidingeitherhigh-voltage(HV)capabili-ties and/or high resistivity substrates (HR) have been investigated to develop depletedMAPS(DMAPS)sensors.ThemorematuredevelopmentsareintheTowerJazz,LFoundry,andAMSprocesses [11]. Two-pixel layout configurations are investigateddependingonthetechnology:onewithsmallcollectionelectrodeandseparatedelectronics,suchasAL-PIDE,andonewithalargecollectionelectrodecontainingtheelectronics.Figure16showsacrosssectionofthetwolayouts.TheformerhasbeendevelopedusingamodifiedversionoftheTJ180nmCMOSimagingprocessusedforALPIDE,whereadeepplanarjunctioninthe epitaxial layer allows for thedepletion region to growbelow the electronics [12].AlargecollectionelectrodeconfigurationisusedinLFoundryandAMStoachievefulldeple-

2Aluminosityof1034cm-2s-1willbringtheinteractionrateto500kHzor1/(2μs).

� �

��

�

�

�

�

����� ����� �����

���������

���������

��� ���� ���

��� ���� ���

����������������

�����������

Figure 2.1: Schematic cross section of a MAPS pixel in the TowerJazz 0.18 µm imagingCMOS with the deep p-well feature.

ALICE ITS Pixel Chip (Sec. 2.3) and briefly present the specifications of the STAR pixeldetector, which is the first large-scale application of CMOS sensors in a HEP experiment(Sec. 2.4). It will be shown that the state-of-the-art MAPS do not fulfil the ALICE ITSrequirements, which motivates the development of new architectures (Sec. 2.5). Severalprototypes have been developed to optimise the di↵erent parts of the Pixel Chip. Theprototypes and their characterisation are presented in Sec. 2.6. All aspects related to theradiation hardness of the technology and the specific circuits implemented in the ALICEPixel Chip are discussed in Sec. 2.7. The chapter concludes with a summary (Sec. 2.8),giving the prospect for the development of the final chip.

2.1 Detector technology

The 0.18 µm CMOS technology by TowerJazz has been selected for the implementation ofthe Pixel Chip for all layers of the new ITS. Figure 2.1 shows a schematic cross sectionof a pixel in this technology. In the following section, we discuss the main features thatmake this technology suitable, and in some respect unique, for the implementation of theITS Pixel Chip.

• Due to the transistor feature size of 0.18 µm and a gate oxide thickness below 4nm, it is expected that the CMOS process is substantially more robust to the totalionising dose than other technologies (such as 0.35 µm) employed up to now as thebaseline for the production of CMOS sensors in particle physics applications.

• The feature size and the number of metal layers available (up to six) are adequateto implement high density and low power digital circuits. This is essential since alarge part of the digital circuitry (e.g. memories) will be located at the periphery ofthe pixel matrix and its area must be minimised to reduce the insensitive area asmuch as possible.

• It is possible to produce the chips on wafers with an epitaxial layer of up to 40 µmthickness and with a resistivity between 1 k⌦ cm and 6 k⌦ cm. With such a resistivity,a sizeable part of the epitaxial layer can be depleted. This increases the signal-to-noise ratio and may improve the resistance to non-ionising irradiation e↵ects.

• The access to a stitching technology allows the production of sensors with dimensionsexceeding those of a reticle and enables the manufacturing of die sizes up to a singledie per 200mm diameter wafer. As a result, insensitive gaps between neighbouringchips disappear and the alignment of sensors on a Stave is facilitated. This option

J. Phys. G: Nucl. Part. Phys. 41 (2014) 087002 The ALICE Collaboration

12

32

tionofthesensorvolumewithuniformelectricfield.Whilstthesmallcollectionelectrodedesignofferstheadvantageofsmallsensorcapacitance,thedesignwithalargecollectionelectrodecanpotentiallyprovidehigherradiationhardness.

Figure16:Crosssections(nottoscale)ofaDMAPSdetectorwheretheelectronics isplacedoutside(left,[12])andinside(right,[13])thecollectionelectrode.

Table3summarizesthemainfeaturesofstate-of-the-artDMAPSprototypesincommercialHV/HR-CMOStechnologies.TheseprototypeshavebeendevelopedforapplicationattheHL-LHC in theATLAS experiment. Theyhavebeenoptimized to copewith highparticleratesandradiationlevelsandachieveatimeresolutionintheorderoffewtensofns, intherightballparkfortheenvisagedtimestampingcapabilityatanEICvertexandtrackingdetector. For a given analogue performance, configurations with small collection elec-trode,havingasmalldetectorcapacitance,enablethepowerconsumptiontobeminimizedandtodesignmorecompactfront-endelectronics,thusallowingasmallpixelsize.Differ-entreadoutarchitectureshavebeendevelopedtocopewith thehighparticlerates [11].Bothsynchronousandasynchronousreadoutarchitectureshavebeen implemented.Thesynchronous readout architecture is based on a well-known concept used in the FE-I3readout chip for the present ATLAS pixel detector, so-called column drain architecture[14]. Novel asynchronous readout concepts have been developed with the potential ofmatching the timing and rate requirements with a lower digital power consumption.WhilstthechoiceofcollectionelectrodeconfigurationisdrivenbythechosenCMOStech-nology, thechoiceof thereadoutarchitecture is independentof theCMOStechnology inwhichtheDMAPSsensorisimplemented. ALPIDE MALTA TJ-MONOPIX LF_MONOPIX ATLASpix_SimpleExperiment ALICEITS ATLASITkpixelPhaseII(outermostlayersonly)Technology TJ180nm ModifiedTJ180nm LF150nm AMS180nmSubstrateresistivity[kOhmcm] >1(epi-layer18-25um) >2 0.08-1Collectionelectrode small small small large largeDetectorcapacitance[fF] <5 Upto400Chipsize[cmxcm] 1.5x3 2x2 1x2 1x1 0.325x1.6Pixelsize[umxum] 28x28 36.4x36.4 36x40 50x250 40x130Timeresolution[ns] 20x103 25Particlerate[kHz/mm2] 10 103Readoutarchitecture Asynchronous Synchronous,columndrainAnaloguepower[mW/cm2] 5.4 <120 ~110 ~300 N/ADigitalpower[mW/cm2] 31.5/14.8 N/A N/A N/A N/ATotalpower[mW/cm2] 36.9/20.2 N/A N/A N/A N/ANIEL[1MeVneq/cm2] 1.7x1013 1.0x1015TID[Mrad] 2.7 50

33

Table 3: Comparison of state-of-the-art MAPS (ALPIDE) and DMAPS sensors (MALTA [15,16], TJ-MONOPIX [17], LF_MONOPIX [17],ATLASPix [18]), designed respectively forheavy ionandproton-protonexperimentsatLHC.ThepowerfiguresoftheALPIDEsensorrefertotheinner/outerlayersoftheALICEITS[10].Duetotheirrecentdevelopments,somepowerfiguresoftheDMAPSsensorsarenotyetpublished.

It is worthmentioning at this point, thatmore technologies have been investigated forDMAPS development (XFAB, ESPROS, Toshiba, Global Foundries, ST microelectronics,etc.).Thesehavehoweveratthetimeofwritingnotreachedafullymonolithicdesignandexistonlyatthelevelofteststructureswithpartialreadoutcapabilities.Theyarethusnotconsideredinthetable.CurrentDMAPSprototypesprovethatthisdetectorconceptcouldbringtheenvisagedim-provementsforanEICvertexandtrackingdetectorwithrespecttothecurrentbaseline,i.e.theALPIDE,withadedicatedR&Dforthisparticularapplication.Buildinguponcurrentdevelopments,aDMAPSsensor for theEICwouldbenefit fromhavingasmall collectionelectrode,fulldepletion,andoptimizedlowpoweranalogueFEandreadoutarchitecture.Different design optimizationsmight be needed for the inner radii, which require verysmallpixelsizeandverylowmaterial,andforthelargerradii,wheretimestampingcapa-bilitycouldbeaddedattheexpenseofslightlylargerpixelsandincreasedmaterial.Simu-lationsshouldinformtherequirementsintermsofpixelsizeandmaterialatdifferentradiitounderstandwheretimestampingcapabilitycouldbeadded,withoutdegradingimpactparameterandmomentumresolution.DMAPSsensors,withtheappropriateoptimization,couldbeusedaswell inthe forwardandbackwardsilicontrackers,aswellasinthemaintrackerincaseofanall-siliconsolu-tion.Inadditiontothesensortechnologiesdiscussedhere,developmentoflightweightservicesand support structures should attract attention in the EIC detector R&D community, toachievealowmaterialsiliconvertexandtrackingdetector.

4.1.2 ForwardsandBackwardsTrackingTrackingdetectorsintheendcapsingeneralservethepurposetocomplementthecentraltrackeratthelarger|𝜂|whereittypicallydoesnotprovidesufficientnumberofhits,ex-cept probably for the all-silicon configuration. Thesedetectors should covermoderatelylargesurfaceareasbehindtheTPCendcap.Exceptionallyhighspatialresolutionisnotre-allyrequired,althoughinordertohelprecoverreasonablyhighmomentumresolutionatp≈30-50GeV/c in thehadron-goingdirection the50μmspatial resolutionperstation isdesirable.ItisalsobelievedthatinordertofacilitatethereliablehadronPIDintheforwardgaseousRICH, a second setof largeplanar trackingdetectorsbetween theRICHvolumeand theelectromagneticcalorimeterisdesirable.Spatialresolutionisnotaconcernhere,butthe

34

detectorsshouldcoverthesurfaceareaofseveralsquaremeters.ItisassumedthatlargeareaMPGDs(GEMs,Micromegas,µRWELL)canbeusedforthesepurposes.The obvious complicationwith the (very) forward and the (very) backward trackers isvanishingbendingpowerofthesolenoidmagnetfortheshallowscatteringangles.Asanexample, at a pseudo-rapidity𝜂 =3,which corresponds to roughly 100mrad scatteringangle, solenoidprovidesonly10%of itsnominalmaximumB∙dℓ integral in thebendingplane.Therefore,onehastoresorttousingverythindetectors(inordertominimizetheconstantterminthemomentumresolutionexpression)withverysmallpixelsize(inor-dertominimizetheslopeinthissameexpressionwiththehighermomenta).MAPStechnologyisanaturalchoice,withallthebenefitsandallitsdrawbacksconsideredindetailintheprevioussection.ItcanbeshownbydirectMonte-Carlomodellingthat7-8MAPSdiskswith20μmpixelsizeand0.3%radiation lengthper layer installedbetweenthenominalIPandroughlytheTPCendcaplocation(1.0-1.2mawayfromtheIP)canpro-videtherequiredmomentumresolutioninthewholepseudo-rapidityrangeandparticlemomentumrangeofinterestforphysics.Thealternativesolutionisasetofhigh-resolutionGEMtrackerstationsinstalleduptothedistancesof~3.0mawayfromtheIP.Monte-Carlosimulationsshowthatthisconfigura-tionshouldalsoworkbutwoulddefinitelyrequire50μmorbetterspatialresolutionperstation.Even if theMAPSdisksareused for trackingat thevery forwardandverybackward𝜂, onemaywant to complement themwith the fast low-material budget trackers like Cr-GEM,theGEMdetectorvarietywiththecopperlayerremovedfromthefoils.4.1.3 RomanPotsOneoftheflagshipmeasurementsforanEICisthemeasurementofthecross-sectionforDeeplyVirtualComptonScattering(DVCS)throughthereactionchannel𝑒𝑝 → 𝑒>𝑝>𝛾.ThisisanimportantprocessbecauseitgivesaccesstotheGPDsofgluons,allowingustolearnabout their transverse spatial distribution inside the proton.One characteristic of thesereactions is that the proton scatters at a very small angle and near beam energy. Thismakes it challenging todetect theseprotons, as it isnecessary to verify that theprotonremainsintactandtoensureexclusivityofthemeasurement.TheexpecteddistributionsoftheprotonsasafunctionoftheirpolarscatteringangleandmomentumareshowninFigure13forcollisionsatdifferentprotonbeamenergies.Spe-cialized instrumentation isneededtomeasure theprotons thatscatteratsuchsmallan-gles.VariousexperimentsatotherfacilitieshaveimplementedforwardprotontaggersasRomanPotstoaccesstheseprotons.TheRomanPotsneedtobedesignedsuchthattheycanberetractedawayfromthebeamduringinjection,andmovedtowardsthebeamoncestableconditionsareachieved.Thisallowsthedetectorstobeplacedasclosetothebeam

35

aspossible,maximizingtheacceptancetotheseprotons.ThedistancetothecoreofthebeamtowhichtheRomanPotscanbeplaceddependsonthebeamwidthatthelocationofthestation.Previousexperienceisthatthesafeoperatingdistanceisroughly10softhebeamwidthfromthecoreofthebeam.TheRomanPotloca-tionhastobecarefullycoordinatedwiththemachineandmagnetdesigngrouptoensurethereissufficientacceptancethroughthemagnets,aswellassufficientdispersiontopulloff-momentumprotonsoutofthebeamintothedetectorsandasmallenoughbeamsizeatthelocationoftheRomanPotssothattheycanbeplacedascloseaspossibletothebeam.Additional R&D efforts on sensor design are ongoing in regards to the development of"edgeless"sensorsorsensorsthatcanbetailoredtotheshapeofthebeamtofurtherin-creasetheacceptancetothesesmallanglescatteredprotons.Simulationshavebeenperformedtoinvestigatethemomentumrangeneededforameas-urementoftheDVCSprocess.ThisissummarizedinFigure17below,whichshowstheex-pecteduncertaintyonthegluonimpactparameterextractedfromthemeasurementusing10 fb-1 of data and full acceptance over the |t| range indicated in the figure. Figure 17showstheidealcaselistedintherequirements.Figure18andFigure19demonstratethenegativeeffectoftheacceptancetruncationateitherthelowerorhigherendofthestated|t|range,respectively.

Figure17:(Left)AsimulationofthemeasurementofDVCScrosssectionfor20x250GeVep-collisionsrepresentingstatistics from10 fb-1ofdata.Themeasurementalsoassumesanacceptancerangeof0.18<𝑝𝑇<1.3GeV/c.Thebandrepresentsthefittothesimulateddata,alongwithitsassociatedun-certainties. (Right) The translation of the cross-section measurement to the measurement of thestructurefunctionF2withitsassociateduncertainties.

36

Figure18:SameasFigure17,butforanacceptancerangeof0.44<𝑝( <1.3GeV/c

Figure19:SameasFigure17butforanacceptancerangeof0.18<𝑝𝑇<0.8GeV/c

BasicrequirementsontheRomanPotsystemsbasedonsimulationsandknowledgefromotherfacilitiesaresummarizedbelow:

1) InstalledinawarmregionoftheIR.2) ZDCdetectorsrequiredtovetothenuclearbreakup.3) Protonacceptanceintherangeof0.18<𝑝( <1.3GeV/c(0.03<|t|<1.7GeV2).4) Multiple stations may be required to allow for efficient tracking, as well as

greateracceptanceoverawiderrangein|t|.5) AmomentumresolutioncomparabletothatofcurrentlyachievedatSTAR.

37

4.1.4 Low-𝑸𝟐TaggerAccess toawiderangeof therelevantkinematicvariablesareparamount toallow foraflexiblephysicsprogramattheEIC.Thefocusofthissectionisontheavailable𝑄!cover-ageatsmallervalues.The𝑄!ofaneventcangenerallybereconstructedbymeasuringtheangleandenergyofthescatteredelectroninaDISevent(thoughthereareothermethodsavailablethatrelyonthereconstructionofthehadronicfinalstate).Figure20aswellasFigure21showthedistributionofthescatteringangleoftheelectronanditsmomentumasitcorrelatestothe𝑄!oftheeventassimulatedwithPYTHIAfor20GeVelectronscol-lidingwith200GeVprotons.Thedistributionslooksimilarforothercollisionenergies.Astrongcorrelation isobserved.Mostof theeventsat low𝑄!(𝑄!<0.1GeV2)result in theelectronscatteringatverysmallangle(lessthan20fromtheelectronbeamdirection)withamomentumveryclose to thebeammomentum.This implies thatelectrons from theseevents will be outside of the main detector acceptance and thus a dedicated device tomeasurethemisrequired.

Figure20:APYTHIA simulationof20GeVelectrons collidingwith250GeVprotonsdisplaying thecorrelationofthescatteredelectronanglewith𝑄2.

Figure21:APYTHIA simulationof20GeVelectrons collidingwith250GeVprotonsdisplaying thecorrelationofthescatteredelectronmomentumwith𝑄2.

38

Suchadeviceneeds tobe incorporated into themachine IRdesign toensure that theseelectronsaresufficientlypulledawayfromthebeamtodetectthem.Thedetectorneedstohavegoodenergyandpositionresolutionaswellinordertocalculatethescatteringangleoftheelectronandthusreconstructthe𝑄!oftheevent.Additionally,itwouldbehelpfultohaveacombinationoftrackingandelectromagneticcalorimetry,whichwouldassistinve-toingphotonshittingthedetectorandhelpwithelectronidentification.4.2 CalorimetryCalorimeters measure particle energy by total absorption. Electromagnetic ones meas-urethe energyof electrons andphotons as they interactwithmatterproducingelectro-magnetic showers. Hadronic calorimeters measure response to the hadronic showers,which contain both an electromagnetic and a strong interaction component, e.g. fission,knock-off,delayedphotons.4.2.1 ElectromagneticCalorimeters

A typical high-performance ElectroMagnetic (EM) calorimeter is a 2D matrix of light-transparent, homogeneous, crystal blocks with dimensions large enough to contain thecomplete showerof secondaryparticles. Crystal calorimetershavebeenused innuclearandhighenergyphysicsfortheirhighresolutionanddetectionefficiency.Thereadoutofcrystal calorimeters is light-based, and the classical option is photomultiplier tubes.Ad-vancedreadoutconfigurationsincludeAvalanchePhoto-DiodesandSiliconPhotomultipli-ers. Homogeneous electromagnetic calorimeters have been used at, e.g. JLab (PbWO4),KTeV(CsI),BaBarandBelle(CsI(TI)),CMS(PbWO4)andL3(BGO)experiments.Thelattertwoarecomplementedbyhadroniccalorimeters.Table4 lists someof thepropertiesoftheseandfewothersystems.

Mostcalorimetersinhighenergyphysicsaresamplingasthecostofhomogenouscrystaloneswouldbeunaffordable.Samplingcalorimetersconsistofanactive(readout,e.g.scin-tillatororCherenkovradiator)andapassive(absorber,e.g.Pb,Cu,W)component.Theyprovidehighgranularityinbothlateralandlongitudinaldirection,butenergyresolutionissubstantially lower than that of crystal calorimeters.Thekeyparameter for this typeofcalorimeter is thesampling fraction,which is theratioofenergydeposited inactiveandpassive layers. There aremanyways to build sampling calorimeters (“sandwich”, “spa-ghetti”,etc),wherethesandwichtypehasbeenmostpopular.Lightcollectionefficiencyisan important consideration for sampling calorimeters as sampling fluctuations directlyimpactenergyresolution.ThemostpopularsolutionsareSPACAL(Pb,scintillatingfibers)and sandwichwithWave-Length-Shifting (WLS) fibers crossing through (“Shashlik”). InbothcasesthefibersarebundledtothePMT.Examplesofsamplingcalorimetersarepro-videdinTable4.

Technology Experi-

mentDepth Energyresolution Readout

39

NaI(TI) CrystalBall 20X0 2.7%/E1/4 Bi4Ge3O12(BGO) L3 22X0 2%/√E+0.7% CsI KTeV 27X0 2%/√E+0.45% CsI(TI) BaBar 16-18X0 2.3%/E1/4+1.4% SiPMCsI(TI) Belle 16X0 2%/√E SiPMPbWO4 CMS 25X0 3%/√E+0.5%+0.2/E APDPbWO4 Primex 1.75%/√E+1.15% PMTPbWO4 PANDA <2%/√E+<1%(req.) LAAPDPbWO4 NPS <2%/√E+<1%(req.) PMTLeadglass OPAL 20.5X0 5%/√E LiquidKr NA48 27X0 3.2%/√E + 0.42% +

0.09/E

Table4:ExamplesofhomogeneousEMcalorimetersystemsbasedoncrystals[19,20,21,22,23,24,25,PANDA,NPS],leadglass[26]ornoblegasliquids[27,28].

Technology Exp. Depth EM Energy resolu-tion

Readout

Scintillator/depletedU ZEUS 20-30X0 18%/√E PMTScintillator/Pb CDF 18X0 13.5%/√E+2.5% Scintillator fiber/Pb spa-ghetti

KLOE 15X0 5.7%/√E+0.6% PMT

LiquidAr/Pb NA31 27X0 7.5%/√E + 0.5% +0.1/E

LiquidAr/Pb SLD 21X0 8%/√E LiquidAr/Pb H1 20-30X0 12%/√E+1% LiquidAr/depl.U D0 20.5X0 16%/√E + 0.3% +

0.3/E

LiquidAr/Pbaccordion ATLAS 25X0 10%/√E + 0.4% +0.3/E

Scintillator/Pb CLAS 15X0 10%/√E PMTScintillator/Pb GluEx 15X0 SiPM

Table5:ExamplesofsamplingEMcalorimetersystemsbasedonlayersoflowX0passivematerialin-terleavedwith activematerial based on plastic scintillators [29, 30, 31, 32], gas [33, 34], silicon +densematerials(Fe,Pb,W,…).Theenergyresolutiondependsonsamplingfluctuations.

TheregionsandfunctionsoftheEMcalorimetersenvisionedfortheEICare:1. Lepton/Backwarddirection:detectthescatteredleptonwithhighenergyreso-

lution. At rapidities 𝜂 ≲ −2 the electron energy measurement comes mainly

40

fromthecalorimeter.Thesegmentationhastobegoodenoughforparticleiden-tification,e.g.toseparateelectronandphotonfromDVCSevents.

2. Ion/Forwarddirection:detect high-x SIDISparticles and the electromagneticpartofhigh-xjetswithhighresolution.

3. Barrel/Mid rapidity: provide particle identification for leptons in a regionwherethehadronbackgroundislarge.TheseincludephotonsfromDVCS,vec-tormesons,p0andelectromagneticpartofjets.

4.2.1.1 BarrelCalorimeterThechoiceofcalorimetryatcentralrapidityisdrivenbytheneedtoprovideelectroniden-tificationinaregionwherethehadronbackgroundislarge.Measuringtheratiooftheen-ergyandmomentumofthescatteredlepton,typicallygivesareductionfactorof~100forhadrons.Inthisregiontheenergy(momentum)measurementisprovidedbytrackingde-tectors,andthusnoticeablyworseenergyresolutionofthecalorimetersuffices.Depending on the center-of-mass energy the rapidity distributions for hadrons (bothchargedandneutral)andthescatteredleptondooverlapandthusneedtobedisentangled(seeFig.10).Thekinematicregioninrapidityoverwhichhadronsandphotonsneedtobesuppressedwith respect to electrons depends on the center-of-mass energy. For lowercenter-of-massenergies,electron,photonandchargedhadronratesareroughlycompara-bleat1GeV/ctotalmomentumand𝜂 =-3.Forthehighercenter-of-massenergy,electronratesareafactorof10-100smallerthanphotonandchargedhadronrates,andcompara-bleagainata10GeV/ctotalmomentum.Thekinematicregioninrapidityoverwhichhad-ronsandalsophotonsneed tobe suppressed, typicallybya factorof10 -100, shifts tomorenegativerapiditywithincreasingcenter-of-massenergy.To satisfy the Particle Identification requirements in the barrel, EM calorimetry shouldprovide:

1. Compactdesignasspaceislimited2. Energyresolution<(10-12%/√E)

There is no need in 2Dprojectivity. It is anticipated that a sampling calorimeter designwithrelativelymodestspecificationswouldmeettherequirements.4.2.1.2 ForwardsandBackwardsCalorimeterThechoiceofcalorimetryatbackwardrapidity-4<𝜂<-1isdrivenbytherequirementtodetectthescatteredleptonwithhighenergyresolution,whichforrapidities|𝜂|>3.5isde-terminedbytheEMcalorimeteralone.Furthermore,thegranularityofthecalorimeterhasto be good enough for particle identification, e.g. to separate electron and photon fromDVCS.Calorimetryatforwardrapidity1<𝜂<3.5isdrivenbytheneedtoidentifyhadronsproducedinsemi-inclusiveprocesses,inparticularatlarge𝑥.

41

Figure9showedthemomentumvs.rapiditydistributionsinthelaboratoryframeforpho-tonsoriginating fromdeeplyvirtualCompton scattering (DVCS) fordifferent leptonandprotonbeamenergycombinations.Forlowerleptonenergies,photonsarescatteredintheforward(ion)direction.Withincreasingleptonenergy,photonsincreasinglypopulatethecentralregionofthedetector.Atthehighestleptonbeamenergies,photonsareevenpro-ducedbackward(inthelepton-goingdirection),veryclosetotheelectroncluster.Overall,as already statedearlier, aEMcalorimetry rapidity coverageof -4<𝜂 <1 isneeded forDVCSphotons.Figure22shows the impactofhigh-resolutioncrystalcalorimetryon(𝑥,𝑄!)determina-tion at small scattering angles,where the tracking resolution is poor.Thequality of thephysicsmeasurementisdeterminedtoalargeextentbythelevelofbin-to-binmigrationinthe2D(𝑥,𝑄!)kinematicplane.Thepastexperience,inparticulartheHERMESCollabo-rationdataanalysis,indicatesthatacceptable“binsurvival”level(theprobabilitytoregis-tertheeventinthesamekinematicbinwhereitoriginallyoccurred),whicheffectivelyde-terminesthekinematicreach,shouldbeofontheorderofatleast0.6-0.7,spanningfromthemaximumvaluesofydowntotheregionofy~0.01(whereyistheDISvariable,de-scribingafractionofthebeamelectronenergycarriedbythevirtualphoton).Asignificantfractionofthe“smally”kinematicdomainischaracterizedbysmallelectronscatteringan-glesandlargeenergy.Asdiscussedabove,trackermomentumresolution,whichistypical-lyusedforthescatteredelectrontrackparameterdetermination,degradesrapidlyunderthesecircumstancesbecauseofthevanishingeffectiveB*dlintegralofthecentralpartofthesolenoidfield.Acrystalcalorimeterwiththesufficientlyhighenergyresolutionintheelectron-going direction end-cap can potentially circumvent this problem. Namely thescatteredelectronmomentumcanbetakenasaweightedmeanofthemomentummeas-uredbythetrackersystemandtheenergymeasuredbysuchacalorimeter.Ahighresolu-tioncrystalcalorimeterfor𝜂 <-2(PWOcrystals)improvestheavailable𝑦rangeconsider-ably.Atrapidity-2<𝜂<1theresolutionsrequirementcanberelaxed.Theoptimalsolu-tionwouldthusbeacombinationofaninner(PWOcrystal)andouter(sampling)calorim-eter.Overall,theinnerEMendcapcalorimeterforrapidity𝜂 <-2shouldprovide:

1. Goodresolutioninangletoatleast1degreetodistinguishbetweenclusters,2. Energyresolution<(1.0-1.5%/√𝐸+0.5%)formeasurementsoftheclusterenergy,3. Timeresolutionto<2ns4. Clusterthreshold:10MeV5. Abilitytowithstandradiationdowntoat least1degreewithrespect tothebeam

line.

TheouterEMendcapcalorimeterforrapidity-2<𝜂 shouldprovide:1. Energyresolution<7%/√𝐸formeasurementsoftheclusterenergy,2. Compactreadoutwithoutdegradingenergyresolution3. Readoutsegmentationdependingontheangle

42

Modellingalsoshowsthatinordertomakeaclearpositiveimpactonthescatteredelec-tronkinematicsdetermination,acrystalcalorimeter(PbWO4)intheinnerpartoftheelec-tron-goingend-capshouldhaveaconstanttermofatmost~0.5%,whileastochastictermontheorderof1.0-1.5%wouldsuffice.

Figure22: InclusiveDIS eventmigration in the {x,𝑄2}kinematicplane.Pythia20x250GeVevents,externalbremsstrahlung turnedoff.Only theareawith survivalprobability>0.6-0.7 is suitable fortheconclusiveanalysis.Leftpanel:onlythetrackerinformationisusedtocalculatescatteredelectronmomentum.Rightpanel:sameevents,butaweightedmeanofthetrackermomentumandthecrystalcalorimeter energy is used. Calorimeter resolution is taken to be sE/E ~ 2.0%/√E for pseudo-rapiditiesbelow-2.0and~7.0%/√Efortherestoftheacceptance.

4.2.2 HadronCalorimetersTherequirementsonhadroncalorimetryareimposedbythejetenergyresolutionandlin-earityofresponseinthehadron-goingdirection.FortheLHCphysicsprogramthejeten-ergyresolutionrequirements is~3%.HadroniccalorimetryatEIC inthe forwardregion,1<𝜂 <4withastochastictermofthehadronicenergyresolutionof seemstobesufficientfor accessing gluon polarization using di-jets to tag photon-gluon fusion events. Thesestudiesrequirethehighestenergies(√𝑠=141GeV)andluminositytoaccumulatestatisticsat high 𝑝( . The dominant contribution to jet energy resolution at these high energiescomesfromtheconstantterm,whichincludesnonlinearities.Forstudiesatlow𝑝( requir-ingsufficientresolutionatlargexforaccessinginclusivejetcross-sectionsinDIS,thesto-chastic termbecomes important.Foroptimal resolution for jet identification,ahadronicenergyresolutionofbetterthanthatachievedatZEUS(35%/√𝐸)combinedwithlowEMenergyresolutionwouldbepreferable.AtHERA,uncertaintiesatlowandmediumvaluesof𝑄!weredominatedbythejetenergyscaleuncertainties,whichwereontheorderof1-2%andtranslatedinto5-10%uncertaintiesinthecrosssection.

BjSimulated X-510 -410 -310 -210 -110 1

]2, [

GeV

2Si

mul

ated

Q

1

10

210

310

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

y = 0.

01

y = 0.

10

y = 0.

95

BjSimulated X-510 -410 -310 -210 -110 1

]2, [

GeV

2Si

mul

ated

Q

1

10

210

310

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

y = 0.

01

y = 0.

10

y = 0.

95

43

4.2.3 ZeroDegreeCalorimeterFormanydifferentprocesses,collisiongeometriesineA-scatteringcanbedeterminedbyutilizing theZero-DegreeCalorimeter (ZDC).Thenumberof forwardneutronsproducedanddetected in theZDC isexpected tobesensitive to thepath lengthof thepartonandfragmentationof the collidingnucleonalong thevirtualphotondirection in thenucleus.Themaximumpathcorrespondstotheimpactparameterb~0.Thereforethemost"cen-tral"collisionsineAcanbeidentifiedfromtheeventswiththehighestneutronmultiplici-ty.Selectingeventswithcentrality>5%willenhancetheeffectiveAinthereaction,whichiscrucialforanymeasurementsofnon-lineareffectsinQCD.ThisselectionwilleffectivelymaximizenucleareffectsinSIDISeAcollisionssuchasforthedi-hadroncorrelationstud-ies.This factandtherequirementthat the four-momentumtransfert indiffractivereac-tions with a charge exchange is obtained from the neutron, requires a ZDCwithmuchhigherenergyandpositionresolutionthaniscurrentlyachievedatRHIC.Qualitativeesti-matesoftheZDCspecificationsrequirefurthermodellingeffort.4.3 ParticleIDExcellentparticleidentification(PID)isanessentialrequirementforafutureEICdetector.Inparticular,quark flavor separation ismuchmore important for theEIC than formosthigh-energyphysics(HEP)experiments.The impactof this is twofold.First, thePIDsys-temshaveamuchlargerimpactontheoverallconfigurationofthedetector;andsecond,thesynergieswithHEPR&Daremorelimitedthaninthecaseof,forinstance,trackingandcalorimetry.AnotheraspectparticulartotheEIC,isthatthedistributionoffinal-stateparticlesisveryasymmetric(duetothelargedifferenceinenergiesoftheincomingleptonandionbeams),andthatthephysicsofinterestrequiresdetectionandidentificationofparticlesoverthefullangularrange.Providingthiscoveragedespite theasymmetriccollisionsrequiresanintegratedsuiteofdetectorsubsystems.4.3.1 HadronPIDForhadronidentification,theonlytypeofdetectorcapableofprovidingtherequiredmo-mentumcoverage (5-50GeV/c,dependingonpolarangle) isbasedonCherenkovradia-tion – although the same principle can have different implementations, designed to ad-dressthewiderangeofrequirementsinthedifferentpartsofthedetectors–bothintermsofparticlemomentumandavailablespace.Thelowestmomenta(uptoafewGeV/c),canbecoveredbymeasurementofthetime-of-flight(TOF)or𝑑𝐸/𝑑𝑥ingaseouscentraltrack-ers(likeaTPC)alongthechargedparticletrajectory.SimulationsshowthatinordertosatisfythephysicsgoalsoftheEIC,itisdesirabletopro-videπ/Kidentificationinthecentralbarrelupto5-7GeV/c,intheelectron-goingendcapup~10GeV/c, and in thehadron-goingendcaponewouldneedtoreach~50GeV/c.To

44

addresstheoverallhadronidentificationrequirements,anintegratedsolutionisrequired,employingdifferenttechnologiesindifferentpartsofthedetector.Inthehadronendcap,theonlypossibilityofreachingthemaximumrequiredmomentumistouseaRing-ImagingCherenkov(RICH)detectorwithalightgas(CF4orC2F6)asradia-tor.However,inordertoprovidecontinuousPIDcoverage,thisneedstobecomplementedbyaradiatorwithahigherindexofrefraction(suchasaerogel).Thetworadiatorscanbepartofonesystem(adual-radiatorRICH),sharingthesameopticsandreadout,orbeim-plementedastwoseparatesystems.Athirdsystem(TOFor𝑑𝐸/𝑑𝑥)isneededtocoverthelowestmomentumrange,belowthepionthresholdoftheaerogelRICH.Thebestcombina-tionof therefractive indexof thegasandaerogelradiators, themomentumreachof thethirdsystem,andthecorrespondingopticsandelectronicsarebeinginvestigatedaspartoftheongoingEICdetectorR&D.TheidealconfigurationwilldependbothonthetechnicaldetailsofthePIDsubsystem(s),butalsoontheoveralldesignofthedetector(space,mag-neticfield,etc).In the central barrel, themain challenge is to have a compact detector that can cover alarge area at reasonable costwhile providing the desiredmomentum reach. A detectorthatcurrentlycanaddressallthreeoftheserequirementsistheonebasedonDetectionofInternallyReflectedCherenkov light (DIRC).OtherRICHdetectors are less compact andwouldbe too costlydue to the large sensor area thatwouldbeneeded,while the flightpath is too short to obtain the desired performance evenwith the very high-resolutionTOFsystems(yetwith5psresolutionanda1mflightpath,TOFcouldprovidereasonable𝜋/𝐾separationuptoabout5GeV/c).Intheelectron-goingendcap,spaceisconstrainedbythedesiretomakethemosteffectiveuse of the EM calorimeter, which (at least in the inner part) needs to include high-resolutioncrystals(e.g.,PWO4).Thus,thebalanceofthethreecriteria(size,cost,andper-formance) is shifted towardsperformance, anda compact aerogeldetectorbecomes thebestchoice.Amorecompactoptionwithlowerperformance,suchasdiscDIRC,wouldbetechnicallyfeasible,butinthispartofthedetectorspaceisnotasrestrictedasinthebar-rel.4.3.2 ElectronidentificationFor an Electron-Ion Collider, it is also crucial to identify the scattered electron amid abackgroundofnegativelychargedpions.Electronidentificationisalsoimportantforpro-ductionof particles (e.g., charmonia),whichdecay into leptons.Here, themaindetectorsystemis theelectromagnetic(EM)calorimeter,whichprovidese/πseparationover thefullmomentumrange.ThePIDsystemsprimarily intended forhadron identificationcanalsoprovideanimportantsupplementarycapabilityfore/π.Thisisparticularlyimportantat lowmomenta(below2-3GeV/c),wherea largepionbackgroundisexpected,andthesuppressionprovidedbytheEMcalorimeter(~100:1)isnotsufficient.Bycombiningthe

45

EMcalorimeterwithaCherenkovdetector,thissuppressionfactorcanbeincreased,effec-tivelyextendingthekinematicreach.Itwouldalsobepossibletoaddane/πcapabilitytothecentraltracker,forinstanceintheform of a hadron-blind detection (HBD) functionality coupled to a TPC (radial HBDreadoutinthecaseofatypicalTPCwithlongitudinaldrift,oranendcapHBDreadoutinanrTPCconfigurationwiththeradialdrift).SuchanHBDwouldcoverthemomentumrangeofrelevanceforidentificationofthescatteredelectron,butadedicatedrTPCfortheelec-tron-goingendcapwouldrequireasignificantamountofspacethatcouldbeusedforoth-ertrackingtechnologies.Fromthispointofview,extendingthee/πmomentumreachofthe(aerogel)Cherenkovinsteadofaddinganothersystemwouldbeamoreuniversalap-proach.In the hadron-going endcap, in addition to electromagnetic and hadronic calorimetry, alargegasCherenkovdetectorcanalsoprovide𝑒/𝜋separationupto10-15GeV/c.Inordertoaddsupplementaryelectronidentificationathighmomenta,onecouldintroduceatran-sition-radiation detector (TRD), which can perform electron identification in the 2-100GeV/crange.AnadditionalbenefitofaTRDisthatitalsoprovidestrackinginformationintheareabetweenRICHandtheelectromagneticcalorimeter,helpingtoimprovemomen-tumandpositionresolution.4.3.3 DetectortechnologiesIn the following, various detector technologies considered for particle identification aredescribedinsomewhatmoredetail.4.3.3.1 Gas-anddual-radiatorRICHThelargegasRICHinthehadron-goingendcapisoneofthemostimportantsystemsoftheEICdetector,butperhapsalsotheoneofferingmostchoices.Themostfundamentalques-tioniswhethertobuildgasandaerogelRICHdetectorsseparatelyoruseadual-radiatorRICH.However,withineachofthetwocategoriesthereexistsayetanothersetofchoices.The dual-radiator RICH is restricted to having mirrors that reflect the Cherenkov lightoutward (away from thebeam line).This isnecessary, since thenear-beamareaon thehadronsidehasthehighestradiationlevelsintheentiredetector.Thisnotonlycreatesalotofbackgroundhits,but thedose is toohigh for thecurrentlyavailablephotosensors.The additional benefit of this configuration is that Cherenkov light produced in the gasdoesnothavetopassthroughtheaerogel.Toenhance thesignal,onecould filterout theshortestwavelengths fromtheaerogelsothatthecollectedUVlightwouldonlycomefromthegas.TheseshortwavelengthphotonsundergoRayleighscatteringastheypassthroughtheaerogel,losingtheCherenkovangleinformation,andwouldonlycontributetothenoiseifallowedtoreachthefocalplane.Thesimplestopticswouldconsistof sphericalmirrorsarranged insectorswith3D focusing,ensuring that the totalphotosensorarea is small, as this is themain costdriver for this

46

typeofdetector.Whilesimplesphericalmirrorsdonotproducea flat focalplane,whichcanintroduceaberrations,theEICR&Dsuggeststhatthisissuecanbeaddressedinarela-tivelystraightforwardwaybyadjustingthegeometricallayoutofthephotosensors.Anadvantageofthedual-radiatorRICHisthatitiseasytoensurefullcoveragebothinan-gleandmomentum–thelatterbymatchingtherefractiveindicesofthegasandaerogel(n=1.02aerogelandC2F6gasseemstobeaverypromisingcombination).Agas-onlyRICHcan inprinciplebebuilt to thesamegeometryasadual-radiatorRICH.Oneofthereasonsforchoosingagas-onlyRICHistohaveinwardreflectingmirrors(i.e.,towardsthebeam).ThischoicechangestheoverallshapeoftheRICHdetectorfromacyl-inder(“pillbox”)toacone(withoutitstop,andwitharoundedbottom).Dependingontheoverall layoutof thedetector, thismaybeeasierto integratewiththeothersubsystems.Theradiationissueassociatedwithafocalplaneclosetothebeamlineisaddressedbyus-ingGEM-basedreadout,whichismoreradiationhardthanopticalphotosensorssuchasMCP-PMTsorSiPMs.CsIusedasaphotocathodematerialintheGEM-basedschemeissen-sitiveonlyintheUV,makingitareasonablematchforCF4radiator,whichisthelightestofthe gases typically used forCherenkovdetectors.However, since the refractive indexofthegas changes rapidlyat shortwavelengths, andwecannotmeasure the “color”of thephoton,chromaticeffectsbecomeasubstantialsourceofuncertainty.InthescopeofEICDetectorR&Dprogramitwasdemonstratedhoweverthatarelativelyshort(1m)RICHde-tectorofthistypeshouldinprinciplebeabletoprovidep/Kseparationbetterthan3s uptothemomenta40-50GeV/c.An initial comparison carried out between the gas-only and dual-radiator RICH optionsindicatedacomparablemomentumreachusingCF4gasintheformerandC2F6inthelatter–bothfulfillingtheEICrequirements.Themaindifferenceisontheother(low)sideofthemomentumrange.WhencombinedwithanaerogelRICH,thelightergasprovidesanover-lapincoverageonlyinthresholdmodeforπ/KandnotatallforK/p.Ifcontinuouscover-agewouldbedesired,itmaybepossibletofindanalternativegasorgasmixture,withahigherindexofrefraction,butretainingpropertiesliketransparencyintheUV.4.3.3.2 CompactAerogelRICHProximity focusing aerogel RICH detectors provide reasonable performance in a smallfootprint.Thiscanbeimprovedevenfurtherbyusingtwolayersofaerogelwithpreciselymatched indices of refraction to create a focusing effect at the high end of the coveredmomentumrange.However,whilesuchadetectorcouldbeusedfortheEIC,recentR&Dsuggests that cost, size, andmomentum coverage could all be significantly improvedbyusing lens focusing(aFresnel lenswouldbepreferable,butaspherical lenscouldbeanalternative). The latter naturally leads to amodular design (hencemRICH),where eachmodulehasitsownlensandreadout.Themainadvantagesofusingalensisthatitcreatesasmaller,butsharperringimage,andthatitcenterstheringinthemiddleofthephoto-sensorplaneevenifthehitwasinacorner.

47

While thephotosensors require a smallerpixel size (2-3mm), the area canbe reduced,leadingtoimprovedperformanceandreducedcost.Inaddition,alensallowsformoreef-fective focusing, which makes it possible to shorten the module. The modular designmakestheaerogelmRICHveryflexibleandeasytointegratewiththeEICdetector.Italsoallowsforaprojectivearrangement,whichcanreducetheangularrangeofparticletracksimpingingonthedetector.Thisinturnfurtherreducestherequiredsensorarea.OnethingtokeepinmindisthatwhiletheEICR&Dcurrentlyfocusesononerepresentativeconfigu-rationtodemonstratetheperformanceofthemRICH,itwouldbequiteeasytousediffer-entvariationsindifferentpartsoftheEICdetector.Forinstance,whiletheprototypeaimsfor3σπ/Kseparationupto8-9GeV/c,increasingthefocallengthandreducingpixelsizewillmakeamoduleslightlylongerbutimprovetheperformance.Longermodulescanbeusedwherespaceisavailableandperformanceisessential,whileshortermodulescanbeusedwhereintegrationwithothersystemsimposesconstraintsontheoverallgeometry.Inasimilarway,differentmodulescanusedifferentphotosensors.Forinstance,modulesplaced closer to the beam could useMCP-PMTs (which aremore radiation hard),whilemodules furtherawaycoulduseSiPMs(whicharenotsignificantlyaffectedbymagneticfields,regardlessoforientation).4.3.3.3 BarrelDIRCDetectorThisdetectorusestotalinternalreflectioninaverypreciselymachinedandpolishedbarwithhighrefractiveindex(quartz),whichalsoactsasaradiator,tocollecttheCherenkovphotonsonasmallsensorplane.Whilethequartzbarsareexpensive,theycostmuchlessperunitarea than thecheapestphotosensors. Inaddition, thebarsarevery thin (2cm)evenwithsupportstructuresincluded(5-6cm),makingtheDIRCidealforthelargebarrelregionofthecentraldetector,whereradialspaceisatapremium.Thekeytotheperfor-manceofDIRCdetectors lies intheopticsprojectingthephotonsemergingfromthebarontoafocalplane,andthepossibilitytomeasurethetimeofpropagationforthephotons.TheoriginalBaBarDIRCusedsimplepinholefocusing,andthetimingresolutionwasonlyabout2ns,whichwasonlyused to remove theout-of-timebackgroundhits.Relyingonspatialimagingonly(𝑥, 𝑦coordinatesinthefocalplane),itreached3σ𝜋/𝐾separationformomentaalmostup to4GeV/c. Since then thedevelopmenthas taken threepaths.Onewas theadditionof focusingoptics, asdemonstratedby theFDIRCR&Dat SLAC (whichusesmirror-basedoptics).ThesecondisexemplifiedbytheBelleIITOPDIRC,whichreliesprimarily on timing and only has a limited spatial imaging capability.While the perfor-manceoftheTOPiscomparabletothatoftheoriginalBaBarDIRC,itachievesthiswithavery small image expansion volume and compact readout, which was the only way tomakeitfittheBelleIIdetector,whichwasnotoriginallydesignedforaDIRC.Anotherad-vantageoftheTOPschemeisthatitswideradiatorbars(“plates”)arecheaperperunitar-eathanthoseoftheBaBarDIRC.Thethirdpathistocombinespatialimagingwithagoodtiming(betterthan~100ps)toperform3D(𝑥, 𝑦, 𝑡)reconstruction.ThejointPANDAandEICR&Defforthasshownthatthisapproachisfeasibleandpromisestodeliververyhighperformance(4σπ/Kseparationat6GeV/c).TheconfigurationexploredfortheEICusesnewlydevelopedadvancedlensesforfocusing,forasharperringimageandsignificantly

48

increasedphotonyield.Thelens-basedopticsalsoallowsonetouseacompactexpansionvolume,whichfacilitatesintegrationwithothersubsystems.InadditiontoprovidingexcellentPID,theHigh-PerformanceDIRCcouldalsobeusedforprecision event timing. The BaBar DIRC demonstrated that, by comparing the expectedpropagationtimesfromallCherenkovphotonsinaneventtothemeasuredtimesinanit-erativeprocess,theeventtimecanbereconstructedwithaprecisionlimitedprimarilybythetimingresolutionofthesensorsandelectronics.4.3.3.4 Time-of-Flight(TOF)TheroleofTOFmeasurementsistoprovidehadronidentificationatlowmomenta,whereother subsystems (like aerogel-based RICH) run out of stem. Current examples of largeTOFsystemsinusetodaytypicallyachieveO(100ps)resolution,buttheR&Disongoingtoimprovethissignificantly.Severalgroupshaveachieved~5psTOFresolutionusingdetec-torsbasedonMCP-PMT’s.mRPCshavedemonstrated~20pstiming.DevelopmentinTOFtechnologyisalsobeingdrivenbyhighenergyphysics,wheretimingoforder10-30psisrequiredtodealwiththeincreasedeventpileupafterthehigh-luminosityupgradeoftheLHC.As part of thisR&D, LGAD (LowGainAvalanche siliconDetectors) havenowbeendemonstratedtobecapableof<30psresolution.AnEICapplicationcouldbetocoverthesmaller angles (close to the beampipe) for a gas-onlyRICHwhere there is no space toplacemRICHmodules.Thisisalsothelocationwiththelongestflightpath,whichisasim-portantastimingresolutionforachievingacertainlevelofTOFPIDperformance.Atthetypicaldistancesof4mavailableon thehadron-going side, a10psTOFwouldprovideπ/Kseparationupto7GeV,whichcouldpotentiallyprovideallof the lowermomentumcoverage for a gaseousRICH.Goingeven further in rapidity, themomentumof theveryforwardparticles,whichhavealongflightpathnearthebeampipeandarehardtomeas-ureusingamagneticspectrometer,couldalsobeprovidedbyTOF.TOFsystemsrequireastart-time,whichcouldbeprovidedbymeasuringtheeventvertexlocation along the beam line. The ultimate limitation here is the length of the electronbunch,whichise.g.~5mmintheeRHICdesign,translatinginto~15pstiminguncertain-ty.Foreventswithtwoandmoretracksthestarttimecanalsobeself-determinedbyiter-ative Bayesian techniques on the track timing information itself. However this basicallyrequires4p acceptancecoveragebyhigh-resolution timingdetectors,whichcanbecomeprohibitivelyexpensive.ItshouldbenotedthatsometimingisalwaysrequiredattheEICinordertoassociatetheparticletrackwithaspecificbunch,sinceeachbunchhasparticularpropertiessuchasthepolarization. However, in the currently envisioned EIC accelerator scenarios the bunchseparationsarerelativelylarge(500psand~9nsinJLABandBNLimplementations,re-spectively),requiringonlymodesttimingresolutionforthesepurposes.

49

4.3.3.5 TransitionRadiationDetector(TRD)Transition radiation (TR) is emitted when a relativistic charged particle crosses theboundary between twomedia of a radiatorwith different dielectric constants [35]. ThenumberofTRphotonsandthetotaltransitionradiationenergyemittedareproportionaltothe𝛾factor(𝛾 = 𝐸/𝑚)ofthechargedparticle[36].Duetothelargemassdifferencebe-tweenelectronsandhadrons,transitionradiationdetectorscouldbeusedfor𝑒/𝜋separa-tionandcanproviderejectionfactorofabout10-1000[37]inthemomentumrange2-100GeV/cforarelativelysmalldetectorvolume.Typically,amaterialwitha largenumberofboundaries isusedasaTRradiator.Forex-ample,astackofregularlyspacedMylarfoilsseparatedbyairgaps,orsomethingwithir-regularboundariessuchasfoamorfleecematerial.Thetypicalradiatorthicknessisabout~0.15%𝑋'fora1cmofmaterial.DuetotheverysmallTRemissionangle,theTRsignalinadetectorisoverlappingwiththechargedparticleionization(𝑑𝐸/𝑑𝑥).DifferentmethodsandtechnologychoicesexistforTRidentificationand𝑑𝐸/𝑑𝑥separation.Traditionally,MWPCsandstrawtubes filledwithXe-basedmixtures,needed to improvedetectionefficiencyforTRphotons,havebeenusedwithinvariousacceleratorbasedex-periments,butaGEMtracker shouldalsowork,andrespectiveprojectexistswithin thescopeoftheEICDetectorR&Dprogram.4.3.3.6 Hadron-BlindDetector(HBD)TheHBDisathresholdCherenkovdetectorwithCF4gasandaveryspecial layoutoftheGEM readout, which can perform e/π identification from low momenta up to about 4GeV/c,where it onlyproduces signals for electrons, but not for hadrons. In the originalPHENIXHBD,thereadoutwaslocatedonthebarrel.Sincethegasisthesameastheonethatwouldbeused inaTPC, theHBD functionality can inprinciplebecombinedwithaTPCwith longitudinal drift, which has its readout on the endcaps. Aside from cost andcomplexity, therewould be no downside to having such an additional capability in theTPC.ThemomentumrangecoveredbytheHBDwouldalsobeidealfortheelectron-goingendcap.BuildinganHBDwiththereadoutontheendcapsofthecylinderratherthaninthebarrelwouldinprinciplebeeasierbutwouldrequiremorethan0.5mofspaceintheEICdetector, dedicated to HBD. It could also be possible to combine thiswith a radial TPC(rTPC)readout,whichwouldaddtrackingfunctionality.However,whilesmallrTPCshavebeenusedsuccessfullyinsolenoidal(longitudinal)magneticfields,itisnotclearhowwellsuchadevicewouldperformifthedriftradiuswasofthesizeoftheendcaptracker.Thus,whilesuchadevicecouldpotentiallybeveryinterestingforanEIC,asignificantamountofR&Dwouldbeneededtodemonstrateitsfeasibilityandperformance.4.3.3.7 PhotosensorsandElectronics

50

Whilenotadetectorsystemperse,photosensorsandelectronicsareessentialforreachingthecostandperformancegoalsofalltheEICPIDsubsystems.Theconsiderationofpossi-blephoto-sensorsolutions foreachdetectorcomponent isdrivenby theoperationalpa-rametersofthedetector,withcostoptimizationinmind.ThephotosensorrequirementsofaselectionofPIDsubsystemsarelistedinthetablebelow.Inparticular,smallpixelswithindividual readout, good timing evenwith small signals, and tolerance tohighmagneticfieldsand radiationareessential.Thus, theseare the importantR&D items,bothduringthedevelopmentphaseofthedetectorsdescribedabove,aswellas fortheir final imple-mentation.Photomultipliers (PMTs) that are viable candidates for EIC applications are Silicon PMs(SiPMs), Multi-anode PMTs (MaPMTs), commercial Microchannel-Plate PMTs (MCP-PMTs),Large-AreaPicosecondPhotodetectors(LAPPDs),andGaseousElectronMultipliers(GEMs)-thelatterforagas-onlyRICH.

Parameter DIRC mRICH,dRICHGain ~106 ~106Timingresolution ≤100ps ≤800psPixelsize 2-3mm ≤3mmDarknoise ≤1kHz/cm2 ≤5MHz/cm2Radiationhardness Yes YesSingle-photonmodeoperation Yes YesMagnetic-fieldtolerance Yes(1.5–3T) Yes(1.5–3T)Photondetectionefficiency ≥20% ≥20%

Table6.Photo-sensorrequirementsforvarioustypesofEICCherenkovdetectors

Asseen inTable6, thisgroupofCherenkovdetectorssharesimilarrequirements,and itwouldeventuallybepossibletousecommonphoto-sensorsandelectronics,reducingde-velopmentandprocurementcosts.ThemaindifferenceisthattheDIRCrequiresnotonlysmallpixelsize,butalsofasttimingandlowdarkcountrate(DCR).Suchtimingresolutionis satisfied by currently available MCP-PMTs (including LAPPDs), but the electronicswouldalsohave toprovide this capability, even for small signals.TheDCR requirementcurrentlyprecludestheuseofSiPMsfortheDIRC,butthismaybecomepossibleinthefu-tureassensorsperformanceimproves.Radiationhardnessisalsoimportantforallphoto-sensors,butinparticularfortheoneslocatednearthebeamline.ThiswouldnotbeagoodlocationforSiPMs,althoughtheycanbeusedinotherlocationswheretheirmagnetic-fieldtoleranceisbeneficial.Sincethephoto-sensorsarealsothemaincostdriverforthemRICHanddRICH,sensorcostreductionswouldhavealargeimpactontheoverallsystemcost.DevelopmentofGEM-basedphoto-sensorsisalsoimportant. Improvementoftheperfor-mance in theUV isuseful for thegas-onlyRICH.Andalthough itwouldbeanambitiousundertaking,ifaphotocathodewasavailablethatwouldbesensitiveinthevisibleregion,it couldprovidea low-cost, radiation-hardalternative to themore traditionalphotosen-sors.

51

4.4 LuminosityMeasurementsEssential toanyphysicsprogramatanEIC istheprecisemeasurementsofthedeliveredluminosity,better than1%.Themeasurementof the luminosityat thecollisionenergiesunder consideration can be based on measuring bremsstrahlung photons from the ep-scattering, 𝑒𝑝 → 𝑒𝑝𝛾 . This is a well-known calculable QED processwith a large cross-sectionmakingitaprimecandidatetomeasuretheluminosity.Additionally,theradiativecorrections in the relevant energy range are small. This reactionproducesphotons thatareemittedinanarrowconearoundthedirectionoftheincomingelectronbeam,andsothegoalforthismeasurementistomeasurephotonsintheverybackwardregion.Thiscanbe seen in Figure 23, which plots the analytic calculation from QED for the differentialcrosssectionasafunctionofphotonenergy(left)andpolarscatteringangle(right)fordif-ferentbeamenergyconfigurations.

Figure23ThedifferentialcrosssectionforBethe-Heitlerscatteringasafunctionofphotonenergy(left)andscatteringangle(right).Differentcollisionenergiesareshownbythecolor-codinganddescribedinthelegend.AscanbeobservedinFigure23,photonsfromthisprocessgenerallyscatteratsmallangle,where thepeakof thedistribution isaround0.03mrad.Thus, the spreadof theconeofphotonsinthedetectorwillbedominatedbybeameffects,suchastheangulardivergencethatistypicallyafactorof10orsolargerthanthatfromdirectphysicsprocess.Theangu-lardivergencequantifiesthespreadintheangleatwhichthecollisionoccurs. TypicallybeamsattheIParesqueezedtodriveuptheluminosity.The luminosity is directly related to the number of detected photons asℒ = 𝑁@/(𝐴𝜎),whereℒistheluminosity,𝑁@isthenumberofdetectedphotons,𝐴istheacceptancecor-rection for photons in themeasured range, and𝜎 is the integrated cross-section in themeasuredrange.Sincethecrosssectionisaccuratelyknown,themainsourcesofsystem-

52

aticuncertaintyareon𝑁@ ,thenumberofphotonsthatwemeasurecomingdirectlyfromtheelasticep-scattering,andtheacceptancecorrection.Themainrequirementoftheluminositymeasuringsystemistohavesufficientacceptancethroughthemachinetothedetectors.Thisisnotatrivialtaskandrequiresclosecollabo-rationwiththemachinedesigners.Thedetectorsneedtobefairlyradiationhardbecauseof to the large luminosityandhigh intensityofBethe-Heitlerphotons. It is important toreducesynchrotronradiationfluxhittingthedetector.Thedetectoralsoneedstobeableto track the luminosityasa functionof time,so thatchanges in luminosityovereach fillcanbeaccountedfor.4.5 TriggerandDataAcquisitionMISSING

• Streamingvs.triggered• ROElectronics(whatisneededwhatmightexist)• WhereisR&Dneeded?

4.6 PolarizationMeasurements4.6.1 ElectronBeamSystemsneed tobe inplace toquantify thepolarizationof thebeam.Dependingon thespecificsoftheelectronbeamofthemachine,thepolarizationneedstobemonitoredasafunctionoftimeandperbunch.Ifoneinvestsinaninjectionschemethatrequiresmultiplecathodestofillthemachine,thepolarizationmonitoringmustbedoneforeachindividualcathodeasafunctionoftime.Thenaturaloptionforelectronbeampolarizationmeasure-mentsattheenergyandcurrentofthebeamsunderconsiderationisComptonscattering.Underthismethod,circularlypolarizedlaserlightimpingesupontheelectronbeam.Thecross sectionof theCompton interactiondependson thepolarizationof thephotonandelectron.Sincethis isapureQEDprocess, itcanbecalculatedanalytically,givingafunc-tionalformfortheasymmetryinthecrosssectionbetweenthepolarizationcombinationsinthecollisions.Theasymmetrycanbemeasuredbycountingthephotonsproducedwithcollisionswiththedifferentspincombinations,withtheresultsbeingfittotheanalyticalexpressionfortheasymmetry.Thepolarizationisafitparameter,andthuscanbeextract-ed from themeasurement. Themain requirement for such ameasurement is to have aspace foraCompton interactionpoint,wherethe laserhits thebeam.Thisprocessmustalsobeparasitictothebeaminthatthemeasurementneedstohavenoeffectonthebeam.Andtherateofcollisionsmustbesufficientlyhightoobtainpolarizationmeasurementsonthetimescaleofsecondsorminutes.Ahighrateisalsorequiredtominimizesystematicuncertaintiestothesub-percentlevel.

53

4.6.2 ProtonBeamMISSING4.6.3 LightIonBeamsMISSING

5 TheEICR&DProgramIn January2011BrookhavenNational Laboratory, in associationwith JeffersonLab andtheDOEOfficeofNuclearPhysics,announcedagenericdetectorR&Dprogramtoaddressthe scientific requirements formeasurements at a future EIC. The primary goals of thisprogram are to develop detector concepts and technologies that have particular im-portance forexperiments inanEICenvironment,andtohelpensurethat thetechniquesandresourcesforimplementingthesetechnologiesarewellestablishedwithintheEICus-er community. It is also anticipated that the topical detector-type-oriented “consortia”(calorimetry,tracking,PIDandothers)willpartlyformabasisoftheactiveEICcommunityandlateronparticipateinshapinguptheactualEICphysicscollaboration(s).ThisprogramissupportedthroughR&DfundsprovidedtoBNLbytheDOEOfficeofNu-clearPhysics.ItisnotintendedtobespecifictoanyproposedEICsite,andisopentoallsegmentsoftheEICcommunity.Proposalsshouldbeaimedatoptimizingdetectioncapa-bility to enhance the scientific reachof polarized electron-proton and electron-ion colli-sionsuptocenter-of-massenergiesof50-200GeVandepequivalentluminositiesuptoafew times1034 cm-2 s-1. Fundedproposals are selected on thebasis of peer reviewby astanding EIC Detector Advisory Committee consisting of internationally recognized ex-pertsindetectortechnologyandcolliderphysics.Thiscommitteemeetstwiceperyear,tohear and evaluate newproposals, and tomonitor progress of the ongoing projects. Theprogramisadministeredby theBNLPhysicsDepartment. Thisprogramis fundedatanannuallevelof~$1.0M,subjecttoavailabilityoffundsfromDOENP.Thefollowingprojectswereoraresupportedbytheprogram:ID Topic StatusRD2011-1 FiberSamplingCalorimeters MergedintoeRD1consortiumRD2011-3 DIRC-basedPID MergedintoeRD14consortiumRD2011-5 RadiationresistantSiPM ConcludedRD2011-6 Tracking/PID/Simulation MergedintoeRD6consortiumRD2012-3 Forward Tracking: GEM & Microme-

gasRenamedintoeRD3

RD2012-5 Physics Simulations/Physics EventGenerators

Concluded

RD2012-8 Crystal R&D for a forward calorime-ter

Concluded

RD2012-11 Spin-lightpolarimeter Concluded

54

RD2012-12 ForwardRICHdetector MergedintoeRD14consortiumRD2012-13 ForwardEMpre-shower ConcludedRD2012-14 TungstenfiberCalorimeters MergedintoeRD1consortiumRD2012-15 GEMbasedTRD ConcludedRD2013-2 Magneticfieldcloakingdevice RenamedtoeRD2RD2013-5 10PicosecondTOF:MCP-PMTs MergedintoeRD14consortiumRD2013-6 Polarimetry&luminositymonitor RenamedtoeRD12eRD1 EICCalorimeterDevelopment Calorimeterconsortia,ongoingeRD2 A Compact Magnetic Field Cloaking

DeviceConcluded

eRD3 Designandassemblyoffastandlightweightbarrelandforwardtrack-ingprototypesystemsforanEIC

MergedwitheRD6

eRD6 Tracking/PID Trackingconsortium,ongoingeRD12 Polarimeter, LuminosityMonitorand

Low𝑄!-TaggerforElectronBeamConcluded

eRD11 RICH detector for the EIC’S forwardregionparticleidentification

MergedintoeRD14,ongoing

eRD10 R&D Proposal for (Sub) 10 Picosec-ondTimingDetectorsattheEIC

MergedintoeRD14,ongoing

eRD14 ProposalforanintegratedprogramofParticle Identification(PID)challeng-esandopportunitiesforafutureElec-tronIonCollider(EIC)

PIDconsortium,ongoing

eRD15 Aproposal forComptonElectronDe-tectorR&D

Ongoing

eRD16 Forward/Backward Tracking at EICusingMAPSDetectors

Ongoing

eRD17 DPMJetHybrid2.0:ATooltoRefineDetectorRequirementsforeACollisions in theNuclear Shadow-ing/SaturationRegime

Ongoing

eRD18 Precision Central Silicon Tracking &VertexingfortheEIC

Ongoing

eRD20 Developing Simulation and AnalysisToolsfortheEIC

Ongoing

eRD21 EIC Background Studies and the Im-pactontheIRandDetectordesign

Ongoing

eRD22 GEMbasedTransitionRadiationTrackerR&DforEIC

Ongoing

eRD23 StreamingReadout OngoingTable7:ListofpastandongoingR&Dprojects.

Proposals,progressreports,presentations,andthecommitteereportscanbefoundonthefollowingwebsite:https://wiki.bnl.gov/conferences/index.php/EIC_R%25D

55

References

1D.Boeretal.,AreportonthejointBNL/INT/JlabprogramonthesciencecaseforanElec-tron-IonCollider,arXiv:1108.1713.2A.Accardietal.,ElectronIonCollider:TheNextQCDFrontier-Understandingthegluethatbindsusall,'',arXiv:1212.1701[nucl-ex].3F.JacquetandA.Blondel,DESY79/48(1979),inProceedingsoftheStudyofanepFacili-tyforEurope,U.Amaldi(ed.).4S.Bentvelsen,J.EngelenandP.Kooijman,in:W.BuchmullerandG.Ingelman(eds.),Pro-ceedingsoftheWorkshoponPhysicsatHERA,Oct.29-30,1991,Hamburg(DESY,Ham-burg,1992),Vol.1,p.23.5T.TollandT.Ullrich,Phys.Rev.C87,024913(2013)andComput.Phys.Commun.185(2014)1835-1853.6L.Zheng,E.C.AschenauerandJ.H.Lee;Determinationofelectron-nucleuscollisiongeom-etrywithforwardneutrons,Eur.Phys.J.A50(2014)no.12,189,arXiv:1707.80557O.Tsaietal;DevelopmentofaforwardcalorimetersystemfortheSTARexperiment,J.Phys.Conf.Ser.587(2015)no.1,0120538L.Serin,TheATLASHighGranularTimingDetectorforthephaseIIUpgrade,CERNdetec-torseminar,https://indico.cern.ch/event/731927/,June2018.9I.Valinetal,AreticlesizeCMOSpixelsensordedicatedtotheSTARHFT,2012JINST7C0110210TechnicalDesignReportfortheUpgradeoftheALICEInnerTrackingSystem,J.Phys.G41(2014)087002,https://cds.cern.ch/record/1625842?ln=en.11N.Wermes,CMOSdetectorsdevelopment,RD50meeting,https://indico.cern.ch/event/719814/contributions/3022652/,June2018.12W.Snoeysetal,AprocessmodificationforCMOSmonolithicactivepixelsensorsforen-hanceddepletion,timingperformanceandradiationtolerance,NIMA871(2017)90-96.13T.Hemperek,ExplorationofadvancedCMOStechnologiesfornewpixeldetectorcon-ceptsinHighEnergyPhysics,PhDthesis,http://hss.ulb.uni-bonn.de/2018/5035/5035.pdf,March2018.14I.Pericetal,TheFEI3readoutchipfortheATLASpixeldetector,Nucl.Instrum.Meth.A565(2006)178.

56

15T.Kugathasanetal,MonolithicPixelDevelopmentina180nmCMOSfortheouterpixellayersintheATLASexperiment,TWEPP2017,https://indico.cern.ch/event/608587/contributions/2614081/attachments/1523908/2381891/Monolithic_ATLAS_CERN_TWEPP_2017_TK_v1.pdf,September2017.16I.Berdalovicetal,MonolithicPixelDevelopmentinTowerJazz180nmCMOSfortheouterpixellayersintheATLASexperiment,PSD2017,https://indico.cern.ch/event/615961/contributions/2659613/attachments/1519758/2373597/Berdalovic_PSD11.pdf,September2017.17T.Wangetal,DepletedfullymonolithicCMOSpixeldetectorsusingacolumnbasedreadoutarchitecturefortheATLASInnerTrackerupgrade,2018JINST13C03039.18I.Peric,ATLASPixandMuPix8inaH18, AIDAWP6meeting,https://indico.cern.ch/event/666202/contributions/2722295/attachments/1525120/2384448/KIT_ATLASPix_and_MuPix8_in_aH18.pdf,September2017.19M.Kubantsev,“PerformanceofthePrimExelectromagneticcalorimeter”,AIPConf.Proc.867(2006)51.20A.Alavi-Haratietal.,Phys.Rev.Lett.83(1999)22.21D.Boutignyetal.,TheBaBarTechnicalDesignReport(SLAC-R-457).22A.Abashianetal.,Nucl.Inst.Meth.A479(2002)11723CMSCollaboration,TheElectromagneticCalorimeterProjectTechnicalDesignReport(CERN/LHCC/97-33).24M.Aleksa,M.Diemoz,“DiscussionontheelectromagneticcalorimetersofATLASandCMS”,Nucl.Inst.Meth.A732(2013)442.25C.Bebeketal.,Nucl.Inst.Meth.A265(1988)258.26M.Akrawyetal.,Nucl.Inst.Meth.A290(1990)76.27G.D.Barretal.,CERN/SPSC/90-22,SPSC/P253(1990).28V.Fantietal.,Phys.Lett.B465(1999)335.29U.Behrensetal.,Nucl.Inst.Meth.A289(1990)115.30L.Balkaetal.,Nucl.Inst.Meth.A67(1988)272.

57

31M.Adinolfietal.,Nucl.Inst.Meth.A482(2002)363.32A.Antonellietal.,Nucl.Inst.Meth.A354(1995)352.33A.Decampetal.,Nucl.Inst.Meth.A294(1990)121.34B.Aubertetal.,LiquidArgonCalorimetrywithLHCPerformanceSpecifications(CERN/DRDC/90-31).35V.L.Ginzburg,I.M.Frank,“Radiationofauniformlymovingelectronduetoitstransitionfromonemediumintoanother”,JETP16(1945). 36V.L.Ginzburg,V.N.Tsytovich,“TransitionRadiationandTransitionScattering”,Inst.ofPhysicsPublishing,Bristol,1990.37A.Andronic,J.P.Wessels“TransitionRadiationDetectors”,10.1016/j.nima.2011.09.041.Technicalnotes:

• ReferencesarehandledasEndnotes(seeFootnotemenu)andthencross-referenced.Thesuperscriptcross-referenceischangefromNNto[NN]byhand.

• Figureswith2ormoreplotsshouldbesetupandformattedviatables.• DefaultfontisMinionPro.

VersionHistory:v1.0:InitialRelease–October19,2018