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High Energy Spin Physics with the PHENIX detector At RHIC. Dave Kawall, RIKEN-BNL and UMass, for PHENIX Collaboration. Title. Outline. Physics motivation Introduction to RHIC Polarized Source pC Polarimeters Hydrogen Gas Jet Target Introduction to PHENIX PHENIX detectors

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  1. High Energy Spin Physics with the PHENIX detector At RHIC Dave Kawall, RIKEN-BNL and UMass, for PHENIX Collaboration Title Dave Kawall (RIKEN-BNL and UMass)

  2. Outline • Physics motivation • Introduction to RHIC • Polarized Source • pC Polarimeters • Hydrogen Gas Jet Target • Introduction to PHENIX • PHENIX detectors • Local Polarimeters • Run History • Relative Luminosity • Physics Analyses and Results • Neutral Pion ALL, Direct Photons, Charged Pions, Muons, Jets, Lamdbas …. • Single Spin Asymmetries • Summary Dave Kawall (RIKEN-BNL and UMass)

  3. Motivation for the RHIC Spin Program • Proton spin sum rule : • Polarized DIS experiments EMC, SMC, SLAC (E80,E131, E142-E155x), HERMES, COMPASS, JLAB - suggest • Gluon contribution may be large, currently not well constrained • accessible in pDIS from NLO pQCD analysis of scaling violations, and from high-pT hadron pair production in photon-gluon fusion, open charm production • Photons don’t couple to gluons - but polarized hadron collisions can involve at leading order - a new approach • RHIC Spin can run with transverse polarization : investigate transversity/ orbital angular momentum/quark-gluon correlations in proton • Parity violation in W production : allows flavor separation Dave Kawall (RIKEN-BNL and UMass)

  4. RHIC Spin : Colliding beams of polarized partons a c Hard Scattering Process b X • Collide beams of polarized protons, 50+% polarization, sqrt(s)=200 GeV • At high pT, sqrt(s), can factorize as beams of polarized partons a,b • Helicity conservation in cross-section (ab-cX) can imply large analyzing power for some processes • We acquire sensitivity to polarized parton distributions, including gluon • Different processes -> different combinations of a,b,cross-section --> can cross-check our results and interpretation Dave Kawall (RIKEN-BNL and UMass)

  5. RHIC Spin : Colliding beams of polarized partons g+q->g+q • Need to measure helicity dependent yields, N, Polarization, P, and Relative Luminosity, R Dave Kawall (RIKEN-BNL and UMass)

  6. RHIC Spin : Colliding beams of polarized partons • Interpretation of results relies on pQCD • high pT and sqrt(s) help to reduce dependence on unphysical scales  M. Stratmann, W. Vogelsang) Dave Kawall (RIKEN-BNL and UMass)

  7. PHENIX (and STAR) data well described by pQCD •  cross-section at mid-rapidity well described by NLO pQCD •  cross-section at mid-rapidity well described by NLO pQCD Dave Kawall (RIKEN-BNL and UMass)

  8. RHIC : The World’s only polarized proton collider RHIC pC Polarimeters Absolute Polarimeter (H jet) BRAHMS & PP2PP PHOBOS Siberian Snakes Siberian Snakes PHENIX STAR Spin Rotators (longitudinal polarization) Spin flipper Spin Rotators (longitudinal polarization) Solenoid Partial Siberian Snake Pol. H- Source LINAC BOOSTER Helical Partial Siberian Snake AGS 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipole AGS pC Polarimeters Strong AGS Snake installed and commissioned during in 2004 run installed in 2005 and to be commissioned to be commissioned • Luminosity ~ 1x1031 cm-2sec-1 at Sqrt(s) = 200 GeV, P ~ 50% • L ~ 2x1032 cm-2s-1, P ~ 70% in the future Dave Kawall (RIKEN-BNL and UMass)

  9. RHIC Optically Pumped Polarized Ion Source (OPPIS) Cryopumps SCS solenoid Rb cell Pump laser Probe laser 28 GHz ECR Proton Source Na jet ionizer cell • Polarized proton blowtorch : 80+ % polarization, ~1 mA H-, 200 microsecond pulses at 7.5 Hz -> 4x1011 protons at 200 MeV after RFQ and Linac Dave Kawall (RIKEN-BNL and UMass)

  10. Proton Beam Polarimetry : pC CNI Polarimeter • CNI : analyzing power, AN, from interference of hadronic non-spin flip and EM spin flip amplitudes • In p-Carbon, AN ~ 1-2% • Need 107 events - but cross section large - just takes a few minutes • AN absolute calibration from elastic pp scattering from polarized H gas jet target • PB measured several times per store Dave Kawall (RIKEN-BNL and UMass)

  11. Absolute polarimetry with Polarized Hydrogen Gas Jet Target • Polarized hydrogen jet target for calibration of pC polarimeters • Thickness : ~ 1.3 x 1012 atoms/cm2 • Polarization : 93% +1/-2% (uncertainty from H2 fraction ) • Located at IR 12 • Event rates of a few Hz Dave Kawall (RIKEN-BNL and UMass)

  12. 13 Countries, 62 Institutions, 550 People Dave Kawall (RIKEN-BNL and UMass)

  13. PHENIXDetector • High resolution, limited acceptance • DAQ can record 5 K events/sec • Triggers for rare events • Central tracking : Pad chamber (PC), drift chamber (DC), time expansion chamber (TEC) • Central Arm Calorimeters : PbSc and PbGl, finely segmented • Forward tracking: Muon tracker • Particle ID : Muon ID, RICH, TOF, TEC • Global Detectors: Beam-Beam Counter (BBC) , Zero-Degree-Calorimeter (ZDC) Dave Kawall (RIKEN-BNL and UMass)

  14. PHENIX Polarized Proton Runs Dave Kawall (RIKEN-BNL and UMass)

  15. How the Bunches Collide in RHIC • Same bunches from each ring collide with each other at 78 kHz • Spin pattern alternates with every bunch crossing • Collecting ++,+-,--,-+ simultaneously reduces systematics • 56 crossings in 2001-2004, up to 106 colliding pairs in 2005 • bunch-by-bunch differences in luminosity and vertex distribution are investigated carefully • Spins can be flipped and colliding pairs can be altered Dave Kawall (RIKEN-BNL and UMass)

  16. Dave Kawall (RIKEN-BNL and UMass)

  17. Dave Kawall (RIKEN-BNL and UMass)

  18. Dave Kawall (RIKEN-BNL and UMass)

  19. Blue Yellow Blue Yellow PHENIX Local Polarimeter • Stable spin direction vertical - spin rotators enable longitudinal collisions • PHENIX discovered analyzing power in neutron production at low pT and high xF in pp collisions at Sqrt(s)=200 GeV • Neutrons identified in ZDC + Shower Max Detector ~18 m ZDC ZDC 10cm (±2mrad) Blue beam Yellow beam Spin Rotators Off Spin Rotators On Dave Kawall (RIKEN-BNL and UMass)

  20. PHENIX Specialty : ALL of in Central Arms • ALL of  has contributions from gxg, gxq, and qxq Fractional contributions to  production • (g x g) and (g x q) dominate below pT of ~ 7GeV/c • At low pT, ALL of  depends on (g)2 Dave Kawall (RIKEN-BNL and UMass)

  21. PHENIX Specialty : ALL of  in Central Arms • Identify from 2 invariant mass peak, extract ALL (0 + BG1) and ALL(BG2) • Fit 0 peak and get combinatorial background fraction • Subtract ALL(BG2) from ALL(0 + BG1) to get ALL(0) Dave Kawall (RIKEN-BNL and UMass)

  22. Check for systematic effects by randomly assigning bunch helicity • Expect ALL of shuffled bunches to be zero, width consistent with errors Bunch shuffling 2/NDF ALL 1-2 GeV/c 2-3 GeV/c 1-2 GeV/c 2-3 GeV/c 3-4 GeV/c 4-5 GeV/c 4-5 GeV/c 3-4 GeV/c • All <2/NDF>are ~1 • Consistent with stat. distribution of2/NDF • Widths are consistent with stat. errors(ALL)(Y.Goto) Dave Kawall (RIKEN-BNL and UMass)

  23. PHENIX Specialty : ALL of  in Central Arms PHENIX PRELIMINARY confidence level PHENIX Data Comparison with Theory ->15% ->15% • GRSV-std : best fit to pDIS results • GRSV-max : G(x)=G(x) at Q20=0.4 GeV2 Dave Kawall (RIKEN-BNL and UMass)

  24. PHENIX Specialty : ALL of  in Central Arms • Run 3 and Run 4 data distinguished between GRSV-max and GRSV-std • Run 5 data should be able to distinguish GRSV-std fromALL = 0 4 pb-1, 50% pol. Dave Kawall (RIKEN-BNL and UMass)

  25. Other Measurements : Cross-section and AN of Charged Hadrons • Mid-rapidity neutral pion and charged hadron single transverse spin asym. • AN consistent with zero • Cross section consistent with pQCD • 0.15 pb-1, Pol ~15 +/- 5% Dave Kawall (RIKEN-BNL and UMass)

  26. Upcoming Measurements : ALL of Jets, J/ • ALL of J/e+/-, …. • Spin transfer with  • using many channels provides cross checks to reduce uncertainties, can extend x region we probe g • ALL of jet-like cluster • trigger on photon, sum energy in central arm - get most of a jet • Potential for high statistics, relatively clean theoretical interpretation Dave Kawall (RIKEN-BNL and UMass)

  27. Upcoming Results from 2005 Run 5 : ALL of Charged Pions • ALL of charged pions from 5-15 GeV/c • Charged pions identified by RICH and EMCal hadronic shower • Sensitive to sign of (M. Stratmann) Dave Kawall (RIKEN-BNL and UMass)

  28. Upcoming Measurements : ALL of Direct Photons • direct production dominated by gluon-Compton process : q+g -> q+ • theoretically clean extraction of g, sensitive to sign of g • small cross-section (~1 nb at pT=5 GeV) -> need high luminosity & polarization Dave Kawall (RIKEN-BNL and UMass)

  29. Summary • Spin program well underway : have first measurements of ALL of neutral pions, and AN of neutral pions and charged hadrons • Cross-sections consistent with NLO pQCD • Expect to be able to extract polarized gluon dist. func. • Upcoming results : ALL of neutral pions, direct photons, etas, J/Psi, jets, charged hadrons, spin transfer in  • Collider improvements : Cold snake in AGS -> polarization and luminosity should increase Dave Kawall (RIKEN-BNL and UMass)

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