1. PANIC05 M. Liu1 Probing the Gluon Polarization with A LL of J/  at RHIC Ming X. Liu Los Alamos National Lab (PHENIX Collaboration)

2. PANIC05 M. Liu2 Spin Crisis and Gluon Polarization Proton Spin Puzzle: Asymptotic limit Gluons may play a significant role ! PCAC

3. PANIC05 M. Liu3 Gluon Polarization Measurements: (SI)DIS Semi-inclusive DIS –HERMES @ DESY high-p T hadron pairs –SMC @ CERN high-p T hadron pairs –COMPASS @ CERN high-p T hadron pairs open charm lepton beam  or  nucleon target ** gluon heavy flavor

4. PANIC05 M. Liu4 @RHIC-SPIN Polarized hadron collisions –double longitudinal spin asymmetry –leading-order gluon interactions direct-photon production heavy-flavor production proton beam  or  gluon photon proton beam  or  gluon heavy flavor

5. PANIC05 M. Liu5 The PHENIX Detectors Central Arms –|  | < 0.35,  ~  – ,  , e,  +-,... – Identified –Momentum, Energy Muon Arms –1.2 < |  | < 2.4 –Momentum (MuTr) –Open charm, J/  etc

6. PANIC05 M. Liu6 A New Probe: Heavy Quarks  Sensitive to gluon polarization:  g(x)  Gluon-gluon interaction dominates at LO PHYTHA estimate: GeVCharmBeauty 20095:585:15 50097:392:8 Double spin asymmetry: Decay modes: e + e -,  +  -, e , eX,  X 1.5 2 5 a LL Karliner & Robinett, Phys.Lett.B324 (1994) J/  bb  e  X cc  eX x

7. PANIC05 M. Liu7  J/  production mechanism LO NRQCD: mix of various processes hep-ph/0509335 G. Nayak et al.

8. PANIC05 M. Liu8  J/  production mechanism (cont.) NLO RNQCD: “final state” mixture ratios: fixed from other data Partonic asymmetry for gg  J/  X Teryaev and Tkabladze PRD56(97)7331

9. PANIC05 M. Liu9 NLO NRQCD and PHENIX data Theoretical predictions of J/Ψ production at RHIC are in good agreement with the PHENIX data: COM process dominant –PRD 68 (2003) 034003 G. Nayak, M. Liu, F. Cooper –PRL 93 (2004) 171801 F. Cooper, M. Liu, G. Nayak PHENIX, PRL 92, 051802 (2004)

10. PANIC05 M. Liu10 A LL Measurement with J/  +  - Experimental approach –Polarization=47% (average) –R is from Beam-Beam-Counter scalers –N_Jpsi Yield

11. PANIC05 M. Liu11  J/  Yield Measurements Fill by fill: (N +- - N ++,-- ) –Detector efficiency variation canceled out –Have Open charm, DY and other background (<10%) Gaussian+Exponentia l background –Used to estimate the background under J/Psi peak Dimuon mass distributions  +  -  +(-)

12. PANIC05 M. Liu12 N J/  > 10 per fill 2 sigma cut: 2.78 < Mass < 3.42 = 1.0089(3) Raw Asymmetries Fill by Fill:

13. PANIC05 M. Liu13 Statistical Test Beam polarization shuffling –random beam polarization values –repeat 10,000 times

14. PANIC05 M. Liu14 Background Raw Asymmetry: Left of the peak: 2.0 < Mass < 2.5 A LL (raw)= 0.0107  0.0220 Under the peak: A LL (raw) = -0.0351  0.0318 N = 988  31 Background Estimation Dimuon mass distributions +- ++, --

15. PANIC05 M. Liu15 A LL vs pT Log(x) First spin physics result from J/  - J/  : produced via almost pure gluon fusion - sensitive to gluon polarization

16. PANIC05 M. Liu16 Summary and Outlook First measurement of double spin asymmetry with J/Psi from longitudinally polarized p-p collisions –Almost pure gluon fusion –10k J/psi, statistically limited –Expect x100 more statistics in the future Work in progress –J/Psi polarization measurement –Open charm - much larger statistics from run5 and will tell us more about gluon polarization Need more theoretical work –J/  production mechanism –Polarized gluon PDFs –Excellent QCD test ground with polarization Where does the nucleon get its spin? –Still don’t know … but RHIC-SPIN will help us to find the answer –and we will learn a lot more about the nature of strong interactions

17. PANIC05 M. Liu17  More on J/  Production Mechanism - J/Psi polarization - a key probe? - Spin dynamics in pQCD α= +1: transversely polarized α= -1: longitudinally polarized α= 0: no polarization ++ J/  ** -- hep-ph/0106120 M. Kramer

18. PANIC05 M. Liu18 NRQCD Calculations of A LL NRQCD LO Helicity dependent double-spin asymmetry λ=1 λ=0 GRSV ++ J/  ** -- hep-ph/0509335 G. Nayak et al.