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Spin Physics with PHENIX (an overview, but mainly D G)

Spin Physics with PHENIX (an overview, but mainly D G). Abhay Deshpande Stony Brook University RIKEN BNL Research Center July 28, 2011. Outline. Introduction Relativistic Heavy Ion Collider as a polarized p+p collider A brief overview of the RHIC Spin program

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Spin Physics with PHENIX (an overview, but mainly D G)

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  1. Spin Physics with PHENIX (an overview, but mainly DG) Abhay Deshpande Stony Brook University RIKEN BNL Research Center July 28, 2011

  2. Outline • Introduction • Relativistic Heavy Ion Collider as a polarized p+p collider • A brief overview of the RHIC Spin program • Spin Physics with PHENIX • Recent measurements leading to DG: Impact & limitations • Prospects of improvement in DG @ PEHNIX in near future • The question of anti-quark polarization • Summary & outlook Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  3. Complementary techniques • Polarized DIS discovered and established the nucleon spin crisis: quarks carry a small fraction of nucleon’s spin. Do gluons carry the remaining spin? Previous talk by COMPASS experiment at CERN • Protons are mostly gluons. Why not explore the gluon’s contribution to the nucleon spin by colliding polarized protons? A complementary approach! pDIS p+p Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  4. pC Polarimeters Absolute Polarimeter (H jet) BRAHMS & now ANDY PHOBOS Siberian Snakes Siberian Snakes PHENIX STAR Spin Rotators (longitudinal polarization) Spin flipper Spin Rotators (longitudinal polarization) LINAC 5.9% Helical Partial Siberian Snake BOOSTER AGS Pol. H- Source Internal Polarimeter pC Polarimeter 200 MeV Polarimeter 10-25% Helical Partial Siberian Snake RHIC as a polarized Collider Without Siberian snakes: nsp = Gg = 1.79 E/m ~1000 depolarizing resonances With Siberian snakes (local 180spin rotators): nsp = ½  no first order resonances Two partial Siberian snakes (11 and 27 spin rotators) in AGS Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  5. The RHIC Spin Program • Determination of polarized gluon distribution via multiple probes (p, g, c-cbar,… production) • Measurement of double longitudinal spin asymmetry ALL • THIS TALK (for PHENIX) & C. Gagliardi (STAR) • Determination of anti-quark polarization using production and decay of W+/- [ maximal parity violation] • Measurement of single longitudinal spin asymmetry AL • TALKS BY E. Kistenev (PHENIX) & J. Balewski (STAR) • Systematic study of transverse spin phenomena & their connections to transverse momentum and spatial distribution of partons • Measurement of single transverse spin asymmetries AN • TALKS BY D. Kleinjan (PHENIX) and R. Fatemi (STAR) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  6. Probes available at RHIC Luminosity Low High 500 GeV CM Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  7. Measuring ALL in a collider (N) Yield (R) Relative Luminosity (P) Polarization • Bunch spin configuration alternates every 106 ns • Data for all bunch spin configurations are collected at the same time • Possibility for false asymmetries are greatly reduced Message: Spin measurements at a collider enable exquisite control over false asymmetries due to ultra fast rotations of the target and probe spin. Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  8. DG program at PHENIX Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  9. PHENIX in 2011 Design philosophy: high resolution in limited acceptance, high rate capability DAQ, excellent trigger and DAQ system • Central Arms (|h| < 0.35) Tracking: Drift, Pad Chambers EM Calorimetry: Dfx Dh ~ 0.01 x 0.01 Particle ID: RICH, TOF Si VTX tracker (|h| < 1) • Forward arms: Mu trackers and identifier (1.2 < h< 2.4) Global detectors: Beam-Beam collisions counters, Zero Degree Calorimeters Muon Piston Calorimeter (3.1 < h < 3.9) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  10. Access to DGin p+p collisions: pp  hX PDF Spin dependence From ep (& pp) (HERA mostly) From e+e- (& SIDIS,pp) Df : Dq from pDIS DGto be measured NLO pQCD Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  11. p0s in PHENIX PRD 76, 051106 (2007) • Large cross section, predominantly g-g interactions • 2-ginvariant mass reconstructed using high pT photon triggers Partonic contribution to 0 s=200GeV, ||<0.35 pT (GeV/c) vs. Background fraction under signal 0 pTwBG 2 20% 5 8% 10 5% Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  12. p0 cross section & ALL PRL 103, 012003 (2009) PRD 76, 051106 (2007) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  13. Impact: Early studies by PHENIX PRL 103, 012003 (2009) at m2 = 4 GeV2 Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  14. 0 p0 cross section & ALL PRD 79, 012003 (2009) • Lower CM Energy: accesses higher x • No evidence of significant asymmetry, • Consistent within uncertainties with asymmetry measurements at 200 GeV Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  15. Impact: Global analysis at NLO (I) DSSV: PRL 101, 072001 (2008) • NLO pQCD+ Data from RHIC (p+p), pDIS(inclusive & semi-inclusive) • RHIC (p+p): Included PHENIX p0 at 200 & 62.4 GeV CM and STAR inclusive jets 200 GeV (Run-6) RHIC Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  16. PHENIX p0 (2009, preliminary) Run5 Run6 Run9 Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  17. Other measurements related to DG Most of these measurements “luminosity starved”. Current impact is limited, but anticipated to be impactful in the next few years Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  18. Other measurements (I) PHENIX p+p h +X Un-polarized NLO cross-section calculations compare well with the measured cross sections, in all cases. PRD83,032001(2011) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  19. Other measurements (II) Jets arXiv:1009.4921 Direct Photon Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  20. What’s next for DG investigations @ PHENIX? Substantial uncertainties in DG at low x, accessible by: Accessing a different event geometry Collisions at higher center of mass energy Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  21. Asymmetric x1 & x2: • The Muon Piston Calorimeter (MPC) • 3.1 < h < 3.9, both m arms • EM showers: • For pT < 2 GeV (p02g) • For pT > 2 GeVhelp from simulation • PYTHIA indicates 80% events from p0 x1 x2 pT=0.5 GeV/c … pT=4 (ref.) ||<0.35 Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  22. High hp0: X-section & ALL Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  23. Low x using p+p at 500 GeV CM Cross section measured ALL(p0) analysis in progress xmindependance on CM Energy xmin xmin xmin Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  24. Quark/Anti-Quark Spin: W Physics at RHIC • DS: From DIS experiments, using g* as the probe • Can not distinguish between quark and anti-quark’s contributions • Determined in semi-inclusive DIS (SIDIS) which employ fragmentation functions to tag quark & anti-quark flavors: resulting in large uncertainties DSSV: PRL 101, 072001 (2008) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  25. An alternate method: p+pW +/- Q and Qbar via parity violating production & decay of W+/- Needs identification of charge of the final state lepton • PHENIX: e+/-in the central arm & m+/-in forward arm • Crucial: Measurement of x-section & comparison with the SM Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  26. p + p  W  e + ncross section PHENIX PRL 106, 062001 (2011) Details of W measurements & its decay in to electrons (and progress on doing the same with) muons: in the following talk by E. Kistenev Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  27. Summary • PHENIX has measured double longitudinal spin asymmetries in polarized p+p collisions at 62.4, 200 & 500 GeV • Results indicate small contribution from DG to the nucleon’s spin in the currently measured regions. • Low x access to DG being explored with forward detectors in PHENIX and by raising the collision energy • Future possible Electron Ion Collider would address this naturally & exquisitely (Talk by M. Stratmann) • Other components to the nucleon’s spin budget (anti-quark’s spin contribution & orbital motion: transverse spin results) in this and other sessions. (Talks by R. Fatemi, D. Kleinjan & on EIC T. Horn) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  28. Thanks Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

  29. Impact: Global Analysis at NLO (II) DSSV: PRL 101, 072001 (2008) Abhay L. Deshpande, Nucleon spin studies with PHENIX at RHIC

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