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Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX

Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX. Kensuke Okada (RBRC) for the PHENIX collaboration DIS2007 Munich. RHIC PHENIX. proton beam.  or . △q. L. gluon. photon. △g.  or . proton beam. The first polarized proton collider (up to s= 500GeV).

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Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX

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  1. Study of Proton Helicity Structure in Polarized p+p Collisions at PHENIX Kensuke Okada (RBRC) for the PHENIX collaboration DIS2007 Munich K.Okada

  2. RHIC PHENIX proton beam  or  △q L gluon photon △g  or  proton beam The first polarized proton collider (up to s=500GeV). Gluon in proton interacts in leading order process. Example: direct photon production Proton spin component The missing proton spin component (g) can be probed by the production asymmetries. K.Okada

  3. PHENIX detector Central arm (||<0.35, 2*0.5) Muon arm (1.2< || < 2.4, 2) K.Okada

  4. PHENIX detector Central arm (||<0.35, 2*0.5) Muon arm (1.2< || < 2.4, 2) Collision counter BBC,ZDC Trigger EMCal and/or RICH MPC (forward EMCal) Muon (E>~2GeV) Longitudinal spin collision (s=200GeV)  L(/pb) 0.35 (2003:Run3) 0.12 (2004:Run4) 3.4 (2005:Run5) 7.5 (2006:Run6) pol~60%!! 70 (2008:Run8) (plan) BBC MPC (EMCal) K.Okada

  5. Cross section measurement Un-pol Before going to asymmetry measurements, we need to confirm the applicability of factorized pQCD. • pQCD calculation is used to extract g (for example sensitive x region) • Is the PDF measured by DIS experiments valid for p+p collisions? — Luminosity measurement by our beam-beam counter (BBC)  L = #BBC / BBC BBC is determined by the transverse beam size measurement #BBC rate = BBC L (beam current)2 / (beam size)2 K.Okada

  6. Cross section measurements p0 Dg2 DgDq Dq2 Un-pol 0 (Run2: PRL 91 241803) pQCD calculation works well. K.Okada

  7. Cross section measurements g Run 5 DgDq DqDq (Run3: PRL 98 012002) Un-pol Direct  pQCD calculation works well. K.Okada

  8. Cross section measurements (charm) PRL97 252002: Run5 Un-pol Electron (from Charm, Beauty) pQCD calculation works well. FONLL upper limit K.Okada

  9. Asymmetry measurement RHIC yellow blue Yellow + - + - + - ……… Blue + + - - + + 120 bunches (revolution time = 1.2 [s]) Relative luminosity determined by BBC,ZDC counts Check relative luminosity measurement Using the same hard scattering as the luminosity measurement  Need to check if there is no ALL in BBC  Comparison between BBC and ZDC Check bunch related systematic uncertainty Enough statistics in a bunch  check rate per bunch If it’s not enough  assign random spin pattern  confirm null asymmetry K.Okada

  10. Mid rapidity 0 asymmetry p0 Dg2 DgDq Dq2 0 s=200GeV (1.8/pb) (“7.5/pb” fast track) K.Okada

  11. 0 asymmetry with theory calculations 0 s=200GeV g = 0.42 at Q2=1(GeV/c)2 best fit to DIS data available in 2001 2 analysis It is consistent to g=0 and even negative g. K.Okada

  12. A way to access higher xgluon Lower collision energy ( s=62GeV) Run6 62.4GeV ~0.06 pb-1 Run5 200GeV 1.8 pb-1 x 0.1 instantaneous luminosity, x100 production for the same xT 0 !! Theory applicability at 62 GeV not yet verified by cross section (@s=200GeV) (@s=62GeV) 5 8 2.5 pT[GeV/c] 1.6 K.Okada

  13. Various channels other than 0 Jet components g+g g+q q+q 0  ± h± “jet” Complementary measurements PHENIX Direct photon Central arm MPC (forward EMCal) Muon arm (but not only for muon) g+q photon Heavy particle g+g open charm to e to  For the high precision, Yield & purity open beauty J/ to e+e to + K.Okada

  14. Yield comparison 0: preferred by EMCal trigger small BG at high pT ALL[%] for 1GeV bin  L pol 7.5/pb 60% 65/pb 70% Yield (arbitrarily) 0.2 0.05 2 0.5 20 5 (PHENIX Central Arm) pT[GeV/c] K.Okada

  15. Yield comparison 0 ±: quark flavor dependence Cherenkov turn-on Background rejection 0.2 0.05 2 0.5 20 5 (PHENIX Central Arm) ALL[%] for 1GeV bin  L pol 7.5/pb 60% 65/pb 70% Yield (arbitrarily) pT[GeV/c] K.Okada

  16. Yield comparison 0.2 0.05 0 2 0.5 ± 20 5 Direct  : gluon Compton BG from hadron decay (PHENIX Central Arm) ALL[%] for 1GeV bin  L pol 7.5/pb 60% 65/pb 70% Yield (arbitrarily) Effective yield pT[GeV/c] K.Okada

  17. Yield comparison 0 Yield (arbitrarily) 0.2 0.05 ± 2 0.5  20 5 Electron (charm) : g+g, hard scattering EMCal trigger threshold BG from conversion  (PHENIX Central Arm) ALL[%] for 1GeV bin  L pol 7.5/pb 60% 65/pb 70% pT[GeV/c] Waiting for high statistics. K.Okada

  18. ALL : various channels ± J/ , preliminary result from Run5, and others are under way.  “jet” Complementary measurements to high statistics 0 measurement K.Okada

  19. Di-Hadron Azimuthal Correlations With 0 - h± correlation Possible helicity dependence Run 5 kT asymmetry (out of ~3GeV) Spin-correlated transverse momentum (orbital angular momentum) may contribute to jet kT. Errors are correlated, 1/P2 (~4) is multiplied K.Okada

  20. Summary With RHIC PHENIX, we measured production cross sections of various particles in p+p collisions at s=200GeV. The results confirm our theoretical understanding of hard scattering, which is important for the next step (= measurement of proton spin structure) Double helicity asymmetry measurement of 0 excludes a large △g scenario. From other channels, complementary results will be obtained. Does the angular momentum play a big role? Jet kT asymmetry may be related. The longitudinal polarization program at s=200GeV will be accomplished with about 70pb-1, 70% polarization in 2008. PHENIX detector upgrade project  talk by J. Lajoie session 9 (Apr.19th) K.Okada

  21. backups K.Okada

  22. pQCD Scale Dependence at RHIC p0 data vs pQCD with different factorization scales: Theoretical uncertainty of pQCD calculations in channels relevant for gluon polarization measurements: HERMES (hadron pairs) μ/2 (factorization scale) COMPASS (hadron pairs) μ 2μ RHIC (direct photon) PHENIX (direct photon) PHENIX (inclusive hadrons) Statistical errors only CDF (direct photon) CDF direct photon C. Aidala, COMPASS Workshop, March 19, 2007

  23. K.Okada

  24. 0 Run2 PRL 91 241803 (2003) K.Okada

  25. h± Run2 PRL 95, 202001 (2005) K.Okada

  26. Direct  Run3 PRL 98, 012002 (2007) K.Okada

  27. Electron Run5 PRL 97, 252002 (2006) K.Okada

  28. Yield comparison s=200GeV Yield (arbitrary) K.Okada

  29. ALL of ±at Ös=200GeV Run 5 K. Barish

  30. Plots for preliminary (1) C. Aidala, UMass Amherst, Plenary session 9/26/06

  31. Plots for preliminary (2) C. Aidala, UMass Amherst, Plenary session 9/26/06

  32. Plots for preliminary (3) C. Aidala, UMass Amherst, Plenary session 9/26/06

  33. K.Okada

  34. K.Okada

  35. K.Okada

  36. ALL of jet-like cluster at Ös=200GeV Run 5 g • “Jet” detection: tag one high energy photon and sum energy of nearby photons and charged particles • Definition of pT cone: sum of pT measured by EMCal and tracker with R = (||2+||2) • Real pT of jet is evaluated by tuned PYTHIA

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