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Recent Spin Results from PHENIX and Future Plan

This presentation by Kiyoshi Tanida outlines the spin physics studies conducted by PHENIX, detailing recent results, cross-section measurements, and future plans for detector upgrades. Topics covered include spin structure of the proton, direct photon production, high-pT hadron production, heavy flavor studies, and spin-flavor structure. The PHENIX experiment and detector specifications are also discussed, along with ongoing data analysis and planned measurements.

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Recent Spin Results from PHENIX and Future Plan

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  1. Recent Spin Results from PHENIX and Future Plan RHIC II spin physics workshop Oct. 7, 2005 Kiyoshi Tanida (RIKEN/RBRC) for the PHENIX collaboration

  2. 13 Countries; 62 Institutions; 550 Participants* *as of March 2005

  3. Outline • Overview of spin physics at PHENIX • The PHENIX experiment • Recent spin physics results • Cross section measurements • ALL measurements • AN measurements • Other measurements • Future plans and detector upgrades • Summary

  4. s ++ - s +- ( ) ( ) = s ++ + s +- ( ) ( ) Overview of spin physics at PHENIX • Main Physics Study of spin structure of proton1/2 = 1/2DS + DG + L (DS ~ 0.25) • How to study? ALL -- double spin asymmetry = (parton pol.)2× (aLL in parton reaction)

  5. Examples of reaction channels • Direct photon: g + q  g + q- ~10% contribution from other processes (e.g.`qq  gg) golden channel for gluon polarization- Need high luminosity (> 100 pb-1). • High-pT hadron production- mix of various processes, q+q, g+g, g+q, ...- feasible at relatively small luminosity (~pb-1) • Heavy flavor • W -- spin-flavor structure

  6. PHENIX experiment PHENIX

  7. The PHENIX Detector • Philosophy • high resolution & high-rate at the cost of acceptance • trigger for rare events • Central Arms • |h| < 0.35, Df ~ p • g, p0, e, p+-, ... – Identified • Momentum, Energy • Muon Arms • 1.2 < |h| < 2.4 • Momentum (MuTr)

  8. s = 200 GeV P recorded L recorded LP4 data volume 2001-2002 transverse-spin run 15% 0.15 pb-1 20 TB first polarized proton collisions 2003 longitudinal-spin run 27% 0.35 pb-1 1.5 nb-1 35 TB spin rotators commissioned, AGS p-C CNI polarimeter 2004 commissioning run (longitudinal spin) 40% 0.12 pb-1 3.3 nb-1 AGS warm snake commissioned, gas-jet absolute polarimeter 2005 longitudinal-spin run (w/ short transeverse run) 49.5/44.5% 3.8 pb-1 205 nb-1 262 TB AGS cold snake installed Statistics 2005 – First long longitudinal-spin polarized-proton run Figure of merit (LP4) more than 40 times larger than that of previous runs

  9. Triggers: Photon Electron Muon Min bias (pre-scaled) Recorded luminosity in Run5 Longitudinal: ~4pb-1 Transverse: 0.16pb-1 3.8 pb-1 BBC live Pol : ~50% 0.11 pb-1 BBC scaled Estimated using #BBC live triggers with BBC=22mb

  10. Spin physics results • Cross sections(not exactly spin, but important cross-check for data/theory reliability) • p0 and direct photonBoth agree well withNLO pQCD calc.

  11. ALL measurements • p0: results from Run 3 and 4 • mixture of qq, qg, and gg • sensitive to gluonpolarization, especiallyat small pT • Run 5 data will give by far shorter error bars

  12. PHENIX PRELIMINARY confidence level g = 1.84 g = 0.42 at Q2=1(GeV/c)2 best fit to DIS data data prefers the GRSV-std curve

  13. ALL for “jet” • Jet detection -- Tag one photon, sum observedenergy/momentum nearby (R < 0.3) • Jet pT estimated by simulations (modified PYTHIA)

  14. J/y dimuon mass distribution (Run5 data) • Very clear J/y peak is observed from muon arm m+m+, m-m- m+m-

  15. J/y ALL First spin physics result from Run5 J/y: produced via almost pure gluon fusion Will be sensitive to gluon polarization, now statistically limited.

  16. AN measurements • For p0 and charged hadrons in central arm • Run2 result with ~0.15pb-1, P~15% • Results may provide information on gluon-Sivers with higher statistics available in Run 5 and beyond PRL, in press

  17. AN of very forward neutron --Local Polarimeter ～1800cm PHENIX Collision Point 10cm blue beam yellow beam ±2mrad Dx magnet <AN>=-0.1100.015 very forward: pT ~ 0.1 GeV/c almost no xF dependence Mechanism unknown

  18. AN of very forward neutron --Local Polarimeter rotator off (transeverse) Asymmetry becomes 0 when polarization is longitudinal (given beam pol. by CNI) rotator on (longitudinal)

  19. AN persists at sqrt(s) = 410 GeV yellow backward blue forward raw asymmetry yellow forward blue backward

  20. Other spin results • Spin dependence of transverse momentum of jets • Back-to-back nature of jets is broken by initial/final state transverse momentum kT（e.g., intrinsic kT, soft gluon radiation） • Orbital angular momentum: kT× rintroduces intrinsic kT in the initial state  measurement of jet kT gives an access to parton orbital angular momentum

  21. possible helicity effect kT larger kT smaller Same helicity Opposite helicity We may observe net effect (after averaging over impact factor)

  22. p+p s = 200 GeV 1.5<pT<2.0 Fit = const + Gauss(0)+Gauss() 3.0<pT<4.0  kT Measurement in PHENIX o - h correlation functions in f distribution d+Au Intra-jet pairs angular width : N jT ... fragmentation Inter-jet pairs angular width : F jT  kT ... fragmentation + kT

  23. Helicity Dependence Stat. only Hint of Helicity dependence?  not yet sure Run05 data should yield a definite answer. BS variance (stat. + syst.)

  24. Future plans and detector upgrade • Near future – under analysis • p0 ALL with Run 5 data • ALL of other channels • Note we have more than 40 times better LP4 than before • AN at s=200 GeV and 410 GeV • p0, charged hadrons, forward neutrons, ... • 9 times more LP2 than before in a 3 days run. • Helicity asymmetry of jet kT • AN of jet kT • In order to obtain significant data, we need a long run with radial polarization  planned in Run6

  25. p0 ALL SPIN2004 Y.Fukao

  26. Other ALL prospects Direct photon Jet ALL h, electron, m, L, ...

  27. Boer and Vogelsang, PRD69:094025,2004 2 0 h AN of Jet kT • A probe to access to Sivers functions. • In order to obtain significant data, we need a long run with radial polarization  planned in Run6 From M.Chiu’s talk at SSA workshop

  28. In the future • ALL of direct photon • “Golden Channel” for Dg, high luminosity required • s = 200 GeV until 2009 • s = 500 GeV from 2009

  29. Silicon-vertex upgrade • Barrel silicon vertex tracker • 2 pixel layer + 2 strip layer • displaced vertex measurement for heavy flavor tagging • wider acceptance for jet • Schedule • completion and installation in 2008 summer • commissioning and data taking from 2008-2009 run

  30. Extended x range

  31. Flavor-identified quark polarization • Weak boson measurement • at s = 500 GeV • parity-violating AL measurement

  32. Trigger RPC Locations Muon-trigger upgrade • For W  m at very high luminosity • Resistive plate chamber • Trigger by timing, momentum • Approved NSF-MRI – 1st Arm in 2008, 2nd Arm in 2009

  33. Summary • PHENIX just has taken first long longitudinal-spin polarized-proton collision data in Run5 • > 40 times more effective statistics than before. • Spin physics results currently we have tells the data is promising for p0 ALL and other channels. • First significant data on gluon polarization in proton. • Yet more is to come • Need more luminosity, more polarization • RHIC II is anticipated

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