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(longitudinal) Spin Program at RHIC-PHENIX

(longitudinal) Spin Program at RHIC-PHENIX. K.Aoki for the PHENIX Collaboration Kyoto Univ. / RIKEN Nishina center INPC2007 Tokyo, Japan. Introduction. Proton has spin ½ Its decomposition still not yet understood well.

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(longitudinal) Spin Program at RHIC-PHENIX

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  1. (longitudinal) Spin Program atRHIC-PHENIX K.Aoki for the PHENIX Collaboration Kyoto Univ. / RIKEN Nishina center INPC2007 Tokyo, Japan

  2. Introduction • Proton has spin ½ • Its decomposition still not yet understood well. • Quark spin carries only ~30% of proton spin. – “proton spin puzzle” • The rest should come from gluon spin, and orbital angular momentum of quarks and gluons. • PHENIX longitudinal spin program • Reveal the spin structure of proton, especially Dg (gluon spin contribution to the proton) which still has large uncertaninty. • Through “Double Helicity Asymmetry(ALL)” of particle production (such as p0) in polpp collisions • gluons participate in leading order. suitable to probe gluon spin! • RHIC -- the world’s first polarized pp collider K.Aoki (Kyoto Univ. / RIKEN)

  3. ALL (of p0) in pol. pp collisions • Theoretically • N: particle yield • P: polarization of beams • R: Relative Luminosity s++= proton Proton’s helicity s+-= jet proton p0 • Experimentally These two processes dominates In our sensitive pT region. strategy • X-section measurement to confirm pQCD applicability • ALL measurement to extract Dg K.Aoki (Kyoto Univ. / RIKEN)

  4. RHIC – the world’s first pol pp collider K.Aoki (Kyoto Univ. / RIKEN)

  5. RHIC – the world’s first pol pp collider Longitudinal spin program Transverse spin program • Talk by M.Chiu (next speaker) (plan) FOM: Figure of Merit K.Aoki (Kyoto Univ. / RIKEN)

  6. RHIC beam at PHENIX IP • Two independent beams(Blue / Yellow) • Bunch structure (120 bunchs in ~106ns interval ) • TransverseLongitudinal at IP (when we need it) • Spin pattern • Syst. uncertainty from time-dep. of the det. eff. avoided. BLUE : + + - - …. Yellow: + - + - …. We can get all possible Collision patterns. K.Aoki (Kyoto Univ. / RIKEN)

  7. BBC ZDC+SMD ( Local Polarimeter ) PHENIX global detector Luminosity Measure • BBC3.0<|h|<3.9 • Quartz Cherenkov det. • ZDC |h|>6.6 (+/- 2.8mrad.) • Hadron Calorimeter These two independent lumi. measure are compared to find out uncertainty on Relative Lumi. Local Polarimetry • SMD (+ ZDC). • Scintillator hodoscopes. • Measures transverse component of beam through AN of neutron. K.Aoki (Kyoto Univ. / RIKEN)

  8. PHENIX Detector • PHENIX has ability to detect various final state particles such as p0,p+-,g,e+- and m+-. Here I concentrate on p0(or g) detection. • |h|<0.35, Df ~ 2 x 90deg • EMCal(PbSc,PbGl) for g measurement. p0 detected via gg decay. • High energy photon trigger available Central Arm beam K.Aoki (Kyoto Univ. / RIKEN)

  9. cross section – pQCD applicability RUN5 200GeV -- p0 arXiv:0704.3599 [hep-ex] RUN5 200GeV – direct g pQCD works K.Aoki (Kyoto Univ. / RIKEN)

  10. cross section – pQCD applicability RUN5 200GeV -- p0 arXiv:0704.3599 [hep-ex] RUN6 62.4GeV -- p0 pQCD works K.Aoki (Kyoto Univ. / RIKEN)

  11. p0 ALL at 200GeV RUN5 200GeV – p0 Submitted to PRL arXiv:0704.3599 [hep-ex] • GRSV theory curves • Std: best fit to DIS data. • DG=G(x),0,-G(x) are also shown DG=G(x),-G(x) are excluded. Dashed / dotted lines corresponds to +-9.4% scale uncertainty. 9.4% Scale uncertainty is not included DG [x=0.020.3] (Q2=1GeV2) K.Aoki (Kyoto Univ. / RIKEN)

  12. p0 ALL at 200GeV RUN6 Run5 prelm. 1.8pb-1 (pol:47%) Run6 prelim. (high pT) 7.5pb-1 (pol:60%) • High pT photon extracted from data virtually online (Lvl.2 filtering) for fast track analysis Significant statistical imrpovement in high pT K.Aoki (Kyoto Univ. / RIKEN)

  13. Access higher x with lower energy pol • Probed xscales with xT • At fixed xT, X-sec is 2 orders of magnitude higher at 62.4GeV than at 200GeV 200GeV prelm. 1.8pb-1 (47%) 62.4GeV prelm. 0.04 pb-1 (48%) Scaling variable Significant statistical improvement in high xT even with small int. lumi can be seen. K.Aoki (Kyoto Univ. / RIKEN)

  14. Various channels available at PHENIX to explore gluon pol. • Jet ( or a component of jet ) • Direct photon • Heavy Flavor g • p0 ,h (gg) • p+- • jet-like cluster g proton proton g q jet proton p0 jet proton p0 g g • g proton q proton • e+- • m+- • J/y (e+e-, m+m-) eor m g D `c proton g c or `cc J/y proton K.Aoki (Kyoto Univ. / RIKEN)

  15. summary • PHENIX longitudinal spin program is to reveal the spin structure of proton, especially Dg which has a large uncertainty. • PHENIX cross-section measurements are shown. The results confirm pQCD applicability which Dg extraction framework relies on. • PHENIX - ALLp0 excludes large |Dg| scenarios. • Statisical improvement expected in the next run. • complementary measurements will be obtained from other channels. • We’ll accumulate 70pb-1(70% pol.) at 200GeV in 2008(RUN8) K.Aoki (Kyoto Univ. / RIKEN)

  16. Back up slides K.Aoki (Kyoto Univ. / RIKEN)

  17. Information on the session • Nucleon Structure II • Session Name:D3, Hall Name:G409 K.Aoki (Kyoto Univ. / RIKEN)

  18. 何故 √s = 62.4GeVがうれしいか？ 62.4 GeV 200 GeV スケーリング 変数 500 GeV [pb/GeV] 測定領域 62.4GeV 200GeV (注）下限は、pT>1GeVの要請から • 同じ xTで比較して、200GeVと比べて２桁大きい。 • 　衝突エネルギーを、 　全て横に持って行った場合。 • 少ない積分輝度で、有意な結果が得られる。 • 高い xTは、高い xをプローブする。 K.Aoki (Kyoto Univ. / RIKEN)

  19. PHENIX Detector – Central Arm K.Aoki (Kyoto Univ. / RIKEN)

  20. PHENIX: g detection.(62GeV) EMCal Trigger • Acceptance - |h|<0.35 , Df=90 x 2 • Energy resolution • Position resolution high energy cluster at EMCal. (~800MeV) w/o BBC • BBC efficiency for p0 event(hard scattering) is low (~40%) p0 reconstruction • Minimal photon energy cut • 0.1 GeV for PbSc • 0.2 GeV for PbGl • Shower profile cut • Energy asymmetry cut • Trigger tile matching. (for higher energy cluster) K.Aoki (Kyoto Univ. / RIKEN)

  21. Longitudinality (62.4GeV) Longitudinal 100% (-2.2%) Transverse 21% (1s uncertainty) ZDC detector neutron What we measure. What we want. Blue beam Forward Blue Beam Backward Horiz-position(cm) Horiz-position(cm) Yellow Beam Forward Yellow Beam Backward Red : Rotator OFF Blue : Rotator ON Horiz-position(cm) Horiz-position(cm) K.Aoki (Kyoto Univ. / RIKEN)

  22. Theory curve by W. Vogelsang K.Aoki (Kyoto Univ. / RIKEN)

  23. Cross section measurements (charm) PRL97 252002: Run5 Electron (from Charm, Beauty) K.Aoki (Kyoto Univ. / RIKEN)

  24. K.Aoki (Kyoto Univ. / RIKEN)

  25. K.Aoki (Kyoto Univ. / RIKEN)

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