ｓPHENIX　 Spin physics Ralf Seidl (RIKEN)

PHENIX upgrades past PHENIX has a history of constant detector improvements Some detectors recently removed for latest upgrades Reaction plan Hadron Blind Detector 11/27/2012 forward sPHENIX

Why do we need to move forward? Longitudinal asymmetries will be measured well in the next few years: Gluon spin at intermediate x First access towards lower x via MPC(+EX upgrade) Sea quark polarizations via W measurements Transverse spin effects largest at forward rapidities ( some addressed already by MPC (clusters) and MPC-EX (p0,photons) Cold Nuclear Matter studies in dAu (possibly also pAu,pU) require lowest xA accessible  most forward Some ideas about diffractive J/y to access GPDs Heavy Ion people also start thinking about forward physics 11/27/2012 forward sPHENIX

Physics motivations – Spin (I) PHENIX, Chiu et al., nucl-ex/0701031 STAR Can we understand the origin of these asymmetries? Pol Beam direction x-Axis Spin Axis BRAHMS Preliminary Large forward single spin asymmetries observed from ZGS, E704 to RHIC in all 3 spin experiments Origins from either initial state (Sivers-like: Qiu-Sterman, Koike-Kanazawa, Kang) or final state (Collins-like: Koike,Kang-Yuan-Zhou ) PRL 101 (2008) 222001 11/27/2012 forward sPHENIX

Separating Sivers and Collins Jet HadronPID Separating Sivers and Collins L-R Asymmetry on parton level jet, photon asymmetries L-R Asymmetry from fragmentation hadron asymmetries in jet 11/27/2012 forward sPHENIX

Jet HadronPID What do we need? Good Jet reconstruction to be able to measure Sivers cleanly Electromagnetic and hadronic calorimetry Particle ID to measure Collins effect Collins effect different for different hadrons RICH B Field to determine charge sign of hadrons 11/27/2012 forward sPHENIX

IFF measurements STAR has first nonzero IFFs seen in pp FFs from Belle IFF evolution known  cleaner access to transversity No TMD so factorization not an issue Need to extend to most forward region for highest x Tensor charge (xBj Integral of quark transversities) 11/27/2012 forward sPHENIX

Physics motivations – Spin (II) e/m ID Transversly polarized Drell Yan (p↑pg*l+l- X ) as important test of TMD QCD formalism: At first glance, SIDIS and Drell-Yan appear to be similar processes with just the photon and quark legs reversed However, color interaction between the initial or final state quark and the proton remnant cause a specific type of factorization breaking: SiversSIDIS = -SiversDrellYan Therefore, measuring Drell-Yan Sivers is a test of our understanding of QCD SIDIS DY 11/27/2012 forward sPHENIX

e/m ID Drell Yan Want to study asymmetries overlapping SIDIS data slightly forward Extend range to unmeasured higher x  most forward 11/27/2012 forward sPHENIX

Drell Yan Expectations show maximal signal at y≥3 (~6 degrees) e/m ID Drell Yan Expectations show maximal signal at y≥3 (~6 degrees) Current Muon arms only go out to h=2.4 (~10 degrees) 3<h<4 is also more difficult: Need field, how large? How do we get particles cleanly (low material budget at shallow angle) Background however die faster than DY (Roughly) PHENIX muon arms sPHENIX coverage 11/27/2012 forward sPHENIX

Sivers DY with TMD evolution e/m ID Sivers DY with TMD evolution Kang’s result from 2012 QCD evolution workshop suggests large evolution effect If Sivers function would really evolve so fast asymmetries would be much smaller than anticipated However, currently not too much known about it need to measure it anyway, but sign change might be more challenging 11/27/2012 forward sPHENIX

Other DY measurements Upolarized pp: u x ubar Boer Mulders e/m ID Other DY measurements Upolarized pp: u x ubar Boer Mulders Single spin p↑p: Transversity x Boer Mulders (combination of u and ubar) Sivers (mostly u) Double spin p↑p↑ , p→p→: u x ubar Transversity (small due to sea) u x ubar Helicity 11/27/2012 forward sPHENIX

The detectors 11/27/2012 forward sPHENIX

The sPHENIX Detector Upgrade Jet PHENIX Collaboration arXiv:1207.6378v1 led by Jamie Nagle, David Morrison & John Haggerty New PHENIX central arms keep VTX inner tracking Magnetic Solenoid: 2 Tesla, 70 cm radius Compact Tungsten-Fiber EMCal Steel-Scintillator Hadronic Calorimeter Open geometry at forward angles for next stage upgrades for transverse spin and eventual ePHENIX 11/27/2012 forward sPHENIX

sPHENIX Forward Physics Jet e/m ID HadronPID The study of transverse spin asymmetries has led to an advanced understanding of scattering processes involving the strong interaction: The PHENIX forward upgrade aims to (1) quantitatively confirm TMD framework including decomposition of AN observed in pp, process dependence and evolution. (2) measure quark transversity dis. including large x  tensor charge ! (3) measure valence and sea-quark Sivers distributions  explore connection to Lz (M. Burkhard arXiv: 1205.2916v1) (4) Survey cold nuclear matter effects in the transition region to the saturation regime. Quantify the initial state for HI-Collisions. TMD framework: inclusion of final and initial state gluon radiation via gauge link integrals gives rise to large transverse spin effects and process dependence. Unique measurements at forward rapidity using jet observables and the Drell-Yan process! 11/27/2012 forward sPHENIX 15 15

Experimental Requirements Driven by p-p Goals Jet e/m ID HadronPID MuID RICH HCal EMCal Tracker Good Jet reconstruction to be able to measure Sivers cleanly Electromagnetic and hadronic calorimetry Particle ID to measure Collins effect and IFF Collins effect different for different hadrons RICH B Field and tracker to determine charge sign of hadrons Electron ID (Preshower) and Muon Id for DY/Quarkonia Vertex detector for heavy flavor tagging 11/27/2012 forward sPHENIX from Kieran Boyle, DIS – April 2012 16

Forward Detector Rely on central magnet field Jet e/m ID HadronPID Rely on central magnet field Studying other field/magnet possibilities EMCal based on restack of current PHENIX calorimetry PbSc from central arm (5.52 cm2) MPC forward arm (2.2 cm2) For tracker considering GEM technology Interest of HI in forward direction may influence choices based on expected multiplicity. PbSc restack MPC restack =12x12 towers 1 tower is 5.5cm2 = 2.2cm2 11/27/2012 forward sPHENIX

Detector Layout for Physics Studies Jet e/m ID HadronPID Detector Layout for Physics Studies Studies for detector components led by GEM-trackers: Los Alamos, RBRC RICH: Stony Brook/RIKEN EMC: RBRC/RIKEN, ISU HCAL: UIUC Magnet: Los Alamos, RBRC, UCR B field might not be enough at highest rapidities  additional magnets needed? 11/27/2012 forward sPHENIX 18

Jet e/m ID HadronPID A dipole detector? Requires beam shielding which might limit acceptance Compensation also necessary Other possibilities? Split dipole like Phobos or similar to LHCb? 11/27/2012 forward sPHENIX

Particle identification e/m ID HadronPID Particle identification Electron reasonable using preshower as photon veto, E/P measurement from EMCAL + tracking Muon identification relatively easy with HCAL + MUID/RPC stations downstream, however reasonable tracking necessary to discard decays Hadron momenta of up to 100 GeV make hadron id difficult with conventional methods, long radiators with low refractive indices necessary, Cherenkov light of difficult wavelength for mirrors and readout 11/27/2012 forward sPHENIX

Other aspects of upgrade Potential of polarized He3 beams Clean access to neutron, but only if protons can be tagged New ideas with ultraperipheral J/Psi production which relates to GPD E, requires scattered proton detection Roman pots : Currently being developed by pp2pp at RHIC 11/27/2012 forward sPHENIX

Next Steps for forward sPHENIX o Detector and sensitivity simulations in progress o RBRC workshop on “Forward Physics at RHIC”  July 30 to August 1st 2012 (https://indico.bnl.gov/conferenceDisplay.py?confId=533) o Initiate exploratory R&D GEM-trackers at Los Alamos (LDRD) EMC at RBRC (RIKEN) HCAL at UIUC (NSF) RICH at SBU/RIKEN? o Report on Physics and Design Studies  March 2013 o Explore funding possibilities: external funds, staging c 11/27/2012 forward sPHENIX 22

Rough x Q2 map for pol. EIC and pp Full eRHIC Transversity and Collins, Sivers: Q2 evolution, Flavor decomposition 1st phase eRHIC High x transversity, High x Sivers pp factorization? D d sign change? Dubar – D dbar, Sivers, Boer Mulders at lower x Forward pp Currend pol DIS JLAB12 Dg via g1 scaling Ds, D sbar 1 10-4 10-3 10-2 0.4 1 xBJ 11/27/2012 forward sPHENIX

Summary Most interesting transverse spin physics and cold nuclear matter effects require detectors with rapidities up to 4 (at RHIC energies) Measurements clearly layed out, currently studying requirements in Simulations R&D phase for several detectors under preparation, re-use current central PHENIX EM calorimetry Golden Spin measurements: Drell Yan Sivers single spin asymmetries Jet (Sivers) and hadron in jet (Collins) single spin asymmetries 11/27/2012 forward sPHENIX