1 / 18

Probing the Gluon Polarization with A LL of J/  at RHIC

Probing the Gluon Polarization with A LL of J/  at RHIC. Ming X. Liu Los Alamos National Lab (PHENIX Collaboration). Spin Crisis and Gluon Polarization. Proton Spin Puzzle: Asymptotic limit. PCAC. Gluons may play a significant role !. lepton beam. g *.  or . heavy flavor. gluon.

sydney
Download Presentation

Probing the Gluon Polarization with A LL of J/  at RHIC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

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

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

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

  5. The PHENIX Detectors • Central Arms • |h| < 0.35, Df ~ p • g, p0, e, p+-, ... – Identified • Momentum, Energy • Muon Arms • 1.2 < |h| < 2.4 • Momentum (MuTr) • Open charm, J/ etc PANIC05 M. Liu

  6. cceX bbeX J/ x A New Probe: Heavy Quarks • Sensitive to gluon polarization: Dg(x) • Gluon-gluon interaction dominates at LO PHYTHA estimate: Double spin asymmetry: Karliner & Robinett, Phys.Lett.B324 (1994) aLL Decay modes: e+e-, +-, e, eX, X 1.5 2 5 PANIC05 M. Liu

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

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

  9. PHENIX, PRL 92, 051802 (2004) 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 PANIC05 M. Liu

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

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

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

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

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

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

  16. 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 PANIC05 M. Liu

  17. + J/ * - 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 hep-ph/0106120 M. Kramer PANIC05 M. Liu

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

More Related