1. Spin Physics at RHIC PHENIX 1.Physics Motivation 2.Accelerator and Detector 3.Result from Run2/Run3 4.What we can do? Atsushi Taketani RIKEN RIKEN Brookhaven Research Center

2. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC2 Physics Motivation

3. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC3 Spin Structure of the Nucleon q What is the origin of the Nucleon Spin? 1/2=(1/2)  +  G+L Q +L G By Deep Inelastic Scattering Experiment  : Quark Spin ~ 0.2-0.3  G : Gluon Spin~ 0 - 2 L Q,L G : Orbital angular momentum ~ ? Polarized proton Collider Experiment

4. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC4 General Idea of Measurement A B a b c d C X UnPol. Case measurement Structure Function pQCD Fragmentation Function Asymmetry

5. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC5 Processes for Probes. Gluon Compton Charmonium Open Heavy Quark Light Flavor High-Pt prompt  e + e -,  +  - e + e -,  +  -,e ,e, ,, Jet (Charged Hadrons, pi0) W boson (Z,Drell-Yan) High-Pt , e, e + e -,  +  - signature Processes W Many processes on P-P collision can be used.

6. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC6 Accelerator and Detectors

7. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC7 Polarized Proton Collider : RHIC AGS LINAC BOOSTER Pol. Proton Source 500  A, 300  s Spin Rotators Partial Siberian Snake Siberian Snakes 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipoles RHIC pC Polarimeters Absolute Polarimeter (H jet) 2  10 11 Pol. Protons / Bunch  = 20  mm mrad P HENIX P HOBOS B RAHMS & PP2PP S TAR Accelerator (ZELENSKI) Polarimeter (BRAVAR and JINNOUCHI ) Detector Local Polarimeter Test set up

8. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC8 PHENIX collaboration 12 Countries 57 Institutions 460 Participants

9. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC9 PHENIX Pioneering High Energy Nuclear Interaction eXperiment PHENIX Detector 1 Central Arm e, g, Charged Hadrons detection | h |<0.35, Df = p 2, Muon Arm m detection 1.2<| h |<2.4, 2 p in f 3, Forward detectors Luminosity Monitoring Local polarimetery Good particle identification High Rate and High Detector granularity. Limited geometrical coverage

10. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC10 Coverage of Detector 0 1 2 3 4 5 Rapidity STAR FPD PHENIX/STAR 0 o CAL PHENIX BBC PHENIX MUON PHENIX CENTRAL STAR TPC pp2pp X F 0.2 0.4 0.6 0.8 PTPT

11. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC11 RHIC Run Summary at PHENIX RUNSpeciesEnergyLuminosityPolarization RUN 1 2000 Au + Au130 GeV1.0/mb RUN 2 2001-2002 Au + Au200 GeV24/mb P + P200 GeV150/nbTransverse RUN 3 2002-2003 Au + Au200 GeV2.7/nb P + P 200 GeV17/nbTransverse 200 GeV350/nbLongitudinal Recorded on tape at PHENIX

12. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC12 ZDC BBC STAR rotators pp2pp Begin of Physics 2 IRs Extension: 180nb -1 /wk, Pola- rization between 0.25 and 0.3. Extended periods with pola- rization above 0.35 earlier in the run. Goal: 500nb -1 /week at P=0.4 Commissioning: 5+3 weeks

13. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC13 Result from RUN2 and RUN3

14. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC14 Central Arm Detector Tracking Detectors 2m ~ 4m from vertex Particle Identification E.M. Calorimeter High granularity

15. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC15 Leading hadrons as jet tags Hard Scattering Process qg+gq qq gg Pt [GeV/c]

16. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC16 p reconstruction at RUN3 2-3 GeV/c Bckgr=17% 3-4 GeV/c Bckgr=7% 4-5 GeV/c Bckgr=5% 1-2 GeV/c Bckgr=45% Results obtained for four pt bins from 1 to 5 GeV/c Pi0 peak width varies from 12 to 9.5 MeV/c 2 from lowest to highest pt bins Background contribution under pi0 peak for  25 MeV/c 2 mass cut varies from 45% to 5% from lowest to highest pt bins 0 A. Bazilevsky will talk.

17. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC17 Gluon Polarization measurement by leading hadrons Estimate with 30pb -1, 70% Pol. Simulation for different charges for different  G h+h+ h-h- A B C 00 h+h+ A LL

18. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC18 Physics of J/  Better understanding of Quantum Chromo- dynamics (QCD) charmonium production includes perturbative QCD aspects non-perturbative QCD aspects (Un-polarized) p+p data are important as reference for heavy ion collision In wide energy range Cross sections Polarization Relative yields (  /  etc) Resolve production mechanism

19. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC19 Muon Arms Geometry Acceptance North : 1.2 <η< 2.4 South: -2.2<η<-1.2 Muon range cut off ~ 2GeV/c m / p rejection ~10^3 Muon Tracker (MuTr) Measurement of momentum Muon Identifier (MuID) Muon identification Trigger Counter North Muon Arm: 2002~ South Muon Arm 2001~ North Muon Arm became operation in 2003 Run Beam μ

20. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC20 J/  Peaks at RUN2 Clear J/  peaks with small background in both e + e - and  +  - pairs N J/  =46N J/  =65

21. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC21  J/  (  s dependence) Energy dependence of  J/  is sensitive to gluon distribution function and its scale Q Our new result and lower-energy results are consistent with typical gluon distribution functions with a reasonable choice of Q  confirms the gluon fusion picture of J/  production in hadron- hadron collisions in a wide energy range

22. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC22  J/  (absolute value) Absolute normalization for  J/  is sensitive to production model –Color-evaporation model (CEM) can explain  J/  using  J/  (fraction of J/  to all produced cc pairs) ~ 0.06 determined by photo-production data –Color-singlet model (CSM) Color singlet production underestimate  J/  by a large (~10) factor –Color-octet model (COM) Consistent using the color octet matrix element +7/M c 2 = 0.02 GeV 3 from photo-production data, but has large uncertainties from Extraction of color-octet matrix element Charm quark mass Factorization and renormalization scales

23. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC23 J/ψ at RUN3 Invariant Mass (GeV) 0312456 First Detection J/ψ with North Muon Arm Data Sample: Dimuon Trigger Integrated Luminosity: 143 nb (~50% of run3pp) Dimuon sample : 3M J/ψ: ~ 227 J/ψ’s Expected number of J/ψ: 600 (North and South) Almost 10 times Statistics ->  Pt, and J/ψ polarization?

24. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC24 XFXF Physics of Forward Detectors FNAL E704 and Qiu-Sterman model Transverse Single Spin Asymmetry ANAN FNAL E704 measured large transverse single spin asymmetry A N Instead Zero expectation from lowest order pQCD calculation Possible origins Initial state interaction Final state fragmentation Higher twist effect Can we use as “Polarimeter”? Let’s measure at RHIC!

25. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC25 Neutron Asymmetry at RUN2 Transverse single spin Asymmetry

26. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC26 ZDC (Zero Degree Calorimeter) at PHENIX RUN3 beam ～ 1800cm 10cm ±2mrad beam -EM and Hadron Calorimeter -> neutron,  Sweep out all charged particles -> only neutron and  Tungsten, Scintillation fiber, 2 layer of tungsten X-Y from fiber, energy deposit from tungsten 5.1λ T 149X 0 (3 ZDC) DX magnet ZDC DX magnet

27. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC27 Measure change of Polarization Vector Raw Asy. / Beam Pol. f -p/2 0 p/2 -p/2 0 p/2 -p/2 0 p/2 Transeverse(Vert.)Transeverse(Horiz,)Longitudinal Evaluate longitudinal component of beam by measuring transverse component of polarization. p  pTpT pLpL Blue = 0.993 K K Yellow = 0.974 K K 0.005 0.000 0.014 0.009 0.013 0.001 0.032 0.009

28. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC28 PHENIX BBC 2 identical parts (BBC-north and -south) Quartz Cherenkov counter 64 segments each. NorthSouth 144.35 cm ⊿ φ = 2π

29. 29 Inclusive Charged Asymmetry in forward region (3<|  |<4) No finite A N was found with looking at charged particle. But Large A N was found in neutron. How about charged particle with neutron tag? Neutron Tag Forward Charged Backward Charged Forward A N = Backward A N = PHENIX preliminary

30. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC30 What’ next?

31. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC31 Prompt photon production Gluon Compton Dominates LO –At LO no fragmentation function –Small contamination from annihilation A1A1

32. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC32 –clear interpretation gluon Compton process dominant statistics with full design luminosity and polarization prompt photon GS95 Gluon polarization measurement by Prompt photon

33. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC33 Physics from Open heavy flavors Provides more independent DG measurements in PHENIX  Helps control experimental and theoretical systematic errors  Different channels cover different kinematic regions bb  e  X direct  cc  eX H. Sato Decay channels:  e + e -,  +  -, e , e, , eD,  D X

34. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC34 A LL in PHENIX using  -e coincidences 320pb -1 data will provide us a lot of e-  coincidences event in PHENIX acceptance 230K from charm and 142K from bottom are expected. At high Pt region, bottom begins to dominate W. Xie & H. Sato simulation 70% polarization

35. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC35 Physics from W production W Asymmetry V-A + helicity conservation when W production 1) Parity violation Good spin analyzer 2) Weak charge Flavor decomposition

36. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC36 Flavor decomposition Note: W + and W -- have a different acceptance In PHENIX. W Z W dominates high Pt m (>20 GeV/c)

37. 2003/09/17 SPIN03Atsushi Taketani RIKEN/RBRC37 In RUN3 PHENIX took longitudinally polarized proton- proton collision data with integrated luminosity 350/nb and average beam polarization 0.3. We measured A LL of inclusive  0 A N from forward detectors PHENIX is well suited to the study of spin physics with a wide variety of probes.  G with prompt , heavy flavor via lepton tag Leading particle from jet Anti-quark helicity distribution via W decay Summary