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The PHENIX Spin Program Recent results & prospects. Kenneth N. Barish Spin Praha 2007 Prague, Czech Rep. July, 2007. Proton Spin Structure at PHENIX. Heavy Flavors. Prompt Photon. Production. Nucleon Spin Structure.  Gluons are polarized ( G )  Sea quarks are polarized:.

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Kenneth N. Barish Spin Praha 2007 Prague, Czech Rep. July, 2007


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    1. The PHENIX Spin Program Recent results & prospects Kenneth N. Barish Spin Praha 2007 Prague, Czech Rep. July, 2007

    2. Proton Spin Structure at PHENIX Heavy Flavors Prompt Photon Production

    3. Nucleon Spin Structure  Gluons are polarized (G)  Sea quarks are polarized: For complete description include parton orbital angular momentum LZ: 1989 EMC (CERN): =0.120.090.14  Spin Crisis Simple parton model: Determination of G and q-bar is the main goal of longitudinal spin program at RHIC

    4. Polarized PDFs from DIS Asymmetry Analysis Collaboration M. Hirai, S. Kumano and N. Saito, PRD (2004) • Valence distributions well determined • Sea Distribution poorly constrained • Gluon can be either positive, 0, negative!

    5. New experimental tool: polarized pp collider Utilizes strongly interacting probes • Probes gluon directly • Higher s  clean pQCD interpretation • Elegant way to explore guark and anti-quark polarizations through W production • Polarized Gluon Distribution Measurements (G(x)): • Use a variety of probes • Access to different gluon momentum fraction x • Different probes – different systematics • Use different energies s • Access to different gluon momentum fraction x

    6. Scattering processes in polarized p+p Hard Scattering Process

    7. pQCD partonic level asymmetries HERMES (hadron pairs) COMPASS (hadron pairs) RHIC (direct photon) E708 (direct photon) CDF (direct photon) • High s and pT make the NLO pQCD analysis reliable • dependence of the calculated cross section on  represents an uncertainty in the theoretical predictions LO • NLO corrections are now known for all relevant reactions M. Stratmann and W. Vogelsang

    8. Leading hadrons as jet tags Hard Scattering Process qg+gq qq gg Double longitudinal spin asymmetry ALL is sensitive to G

    9. RHIC can accelerate polarized protons! RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes BRAHMS & PP2PP PHOBOS 2005 Complete! Siberian Snakes Spin Flipper PHENIX STAR Spin Rotators Partial Snake Approaching design Helical Partial Snake Strong Snake Polarized Source peak average  design L 2.5 1.2 6.0 P 67% 61% 70% LINAC AGS BOOSTER 200 MeV Polarimeter Luminosity in 1031cm-2s-1 Rf Dipole AGS Polarimeter

    10. The PHENIX Detector for Spin Physics • Philosophy (initial design): • High rate capability & granularity • Good mass resolution & particle ID • limited acceptance • p0/g/h detection • Electromagnetic Calorimeter: • p+/p- • Drift Chamber • Ring Imaging Cherenkov Counter • J/y • Muon Id/Muon Tracker • Relative Luminosity • Beam Beam Counter (BBC) • Zero Degree Calorimeter (ZDC) • Local Polarimetry - ZDC • Filters for “rare” events

    11. PHENIX polarized-proton runs Longitudinally Polarized Runs Transversely Polarized Runs ** initial estimate

    12. Total Raw Data Volumes • WAN data transfer and data production at CC-J in RIKEN, Wako Japan • 60MB/s sustained rate using grid • 570 Tb transferred in Runs 5 & 6

    13. I. Gluon Polarization GS95 xDG(x) prompt photon cceX bbeX J/ Robust measurement covering wide xg region through multiple channels: • Results • π0 200GeV – Run 3, 4, 5, 6 (prelim) • 64GeV – Run 6 (prelim) • π± Run 5 (prelim) • Jet-like Run 4, 5(prelim) • h Run 5(prelim) • J/yRun 5, 6 (level2) • Photon Coming soon. See talk by P. Liebing

    14. Measuring ALL • (N) Helicity dependent yields • (R) Relative Luminosity • BBC vs ZDC • (P) Polarization • RHIC Polarimeter (at 12 o’clock) • Local Polarimeters (SMD&ZDC) • 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

    15. 0cross section at 200GeV p0 Dg2 DgDq Dq2 arXiv:0704.3599 [hep-ex] NLO pQCD calculations are consistent with cross-section measurements

    16. p0 ALL PHENIX Preliminary Run6 (s=200 GeV) Statatistical uncertainties are on level to distinguish “std” and “0” scenarios 5 10 pT(GeV) GRSV model: “G = 0”: G(Q2=1GeV2)=0.1 “G = std”: G(Q2=1GeV2)=0.4 Run3,4,5: PRL 93, 202002; PRD 73, 091102; hep-ex-0704.3599

    17. Relationship between pT and xgluon • NLO pQCD: 0 pT=29 GeV/c • GRSV model: G(xgluon=0.020.3) ~ 0.6G(xgluon =01 ) • Note: the relationship between pT and xgluon is model dependent • Each pT bin corresponds to a wide range in xgluon, heavily overlapping with other pT bins • Data is not very sensitive to variation of G(xgluon) within measured range • Any quantitative analysis assumes some G(xgluon) shape Log10(xgluon)

    18. Sensitivity of p0 ALL to DG Scaling Errors not included present x-range xDG(x) GRSV std x • “std” scenario, G(Q2=1GeV2)=0.4, is excluded by data on >3 sigma level: 2(std)2min>9 • Only exp. stat. uncertainties are included (the effect of syst. uncertainties is expected to be small in the final results) • Theoretical uncertainties are not included

    19. Global Analysis One of the attempts of global analysis by AAC Collaboration using PHENIX 0 Run5-Preliminary data Now Run5-Final and Run6-Preliminary 0 and Run5-Preliminary jet data are available • Results from various channels combined into single results for G(x) • Correlations with other PDFs for each channel properly accounted • Every single channel result is usually smeared over x  global analysis can do deconvolution (map of G vs x) based on various channel results • NLO pQCD framework can (should!) be used • Global analysis framework already exist for pol. DIS data and being developed to include RHIC pp data, by different groups

    20. ΔG(x) C from Gehrmann Stirling Extending x-range is crucial present x-range xDG(x) GSC: G(xgluon= 01) = 1 G(xgluon= 0.020.3) ~ 0 GRSV-0: G(xgluon= 01) = 0 G(xgluon= 0.020.3) ~ 0 GRSV-std:G(xgluon= 01) = 0.4 G(xgluon= 0.020.3) ~ 0.25 x 0.3 GSC-NLO: ΔG = ∫0.02ΔG(x)dx ~ small0 Much of the first moment ΔG = ∫ΔG(x)dx might emerge from low x! GSC-NLO: ΔG = ∫ΔG(x)dx = 1.0 GSC-NLO GSC: G(xgluon= 01) = 1 GRSV-0: G(xgluon= 01) = 0 GRSV-std:G(xgluon= 01) = 0.4 GSC: G(xgluon= 01) = 1 GRSV-0: G(xgluon= 01) = 0 GRSV-std:G(xgluon= 01) = 0.4

    21. PHENIX p0 ALL vs GSC-NLO present x-range xDG(x) x NEED TO EXTEND MEASUREMENTS TO LOW x !! GSC-NLO: ΔG = ∫ΔG(x)dx = 1.0 Large uncertainties resulting from the functional form used for ΔG(x) in the QCD analysis! GSC-NLO courtesy of Marco Stratmann and Werner Vogelsang

    22. Extend x Range Extend to higher x at s = 62.4 GeV Extend to lower x at s = 500 GeV • To measure DG, need as wide an x range as possible. • Planned Upgrades will help (see later in this talk) • By measuring at different center of mass energies, we can reach different x ranges. • We can extend our x coverage towards lower x at s = 500 GeV. Expected to start in 2009. • We can extend our x coverage towards higher x at s = 62.4 GeV.  Run6 present x-range s = 200 GeV

    23. p0 ALL @ s=62.4 GeV GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775. • Short run with longitudinal polarized protonsALL • Grey band: systematic uncertainty due to Relative Luminosity

    24. Comparison with 200 GeV • At fixed xT, p0 cross section is 2 orders of magnitude higher at 62.4 GeV than at 200 GeV • Converting to xT, we can get a better impression of the significance of the s=62.4 GeV data set, when compared with the Run5 final data set. Run5 200GeV final 2.7pb-1 (49%) Run6 62.4GeV prelm. 0.04 pb-1 (48%)

    25. Sign Ambiguity Hard Scattering Process p0 DG2 DGDq Dq2 • Dominance of two gluon interaction at low pT  present p0 ALL data cannot determine sign of DG. • Solution: • Higher pT higher FOM (P4L) • Look to other probes: • Charged pions • Direct Photon

    26. Charged pion ALL Fraction of pion production • Charged pions above 4.7 GeV identified with RICH. • At higher pT, qg interactions become dominant and so DqDg term is ALL becomes significant allowing access to the sign of DG

    27. ALL of ±at Ös=200GeV Run 5

    28. Prompt g production at Ös=200GeV g DgDq DqDq • “Golden Channel” • Gluon Compton Dominates • PHENIX well suited, but not easy & requires substantial L & P Run 3 hep-ex/0609031

    29. ALL of prompt gat Ös=200GeV Isolation cut to reduce background Eg signal isolated pi0 photon R ALLg coming soon!

    30. ALL of h and J/y at Ös=200GeV Dg2 DgDq Dq2 h • Complementary to p0 measurement • h fragmentation function not yet available.

    31. II. Transverse Spin (AN) PT MPC XF 0.2 0.4 0.6 0.8 MUON CENTRAL BBC Kinematical Coverage @ 200GeV 0o CAL 0 1 2 3 4 5 Rapidity (Sivers effect) transversely asymmetric kt quark distributions (Collins effect) spin-dependent fragmentation functions (Twist-3) quark gluon field interference • π0/π±/h± • 200GeV – run 2 (published), 5 (prelim) • 64GeV – run 6 (prelim) • J/y • Run6 (level2) • Forward neutron – s,xF dependence • MPC Run6 • 64GeV (prelim) See talk by K. Oleg Eyser

    32. AN of p0 and h± for y~0at Ös=200GeV |h| < 0.35 hep-ex/0507073 (hep-ex/0507073) π0 (2001/02) Run 2 Run 5 pt (GeV/c) pt (GeV/c) PRL 95(2005)202001 • AN is 0 within 1%  interesting contrast with forward p May provide information on gluon-Sivers effect • gg and qg processes are dominant • transversity effect is suppressed

    33. AN of J/yat Ös=200GeV • Sensitive to gluon Sivers as produced through g-g fusion • Charm theory prediction is available • How does J/y production affect prediction?

    34. Muon Piston Calorimeter (MPC) • p0 detection in forward direction • 3.1 < |h| < 3.65 • South arm installed for Run 6 test. • Expect 200GeV longitudinal and 62GeV longitudinal & transverse results • North installed for Run 7 MIP Peak

    35. PLB 603,173 (2004) 0 ANat large xF p+p0+X at s=62.4 GeV p+p0+X at s=62.4 GeV 3.0<<4.0 process contribution to 0, =3.3, s=200 GeV • Asymmetry seen in yellow beam (positive xF), but not in blue (negative xF) • Large asymmetries at forward xF  Valence quark effect? • xF, pT, s, and  dependence provide quantitative tests for theories

    36. III. Future Prospects • High luminosity and polarization • 200 & 500 GeV Running • Upgrades • Muon trigger upgrade • Nose-Cone Calorimeter Upgrade • Silicon barrel and forward upgrade

    37. Neutral pion projections • Spin plan: • 65 pb-1 at √s=200GeV & 70% pol • 309 pb-1 at √s=500GeV & 70% pol see Spin report to DOE http://spin.riken.bnl.gov/rsc/

    38. Prompt photon projections • Spin plan: • 65 pb-1 at √s=200GeV & 70% pol • 309 pb-1 at √s=500GeV & 70% pol see Spin report to DOE http://spin.riken.bnl.gov/rsc/

    39. Physics Impact of PHENIX Upgrades Present vs with upgrades Inclusive hadrons + photons forward heavy flavor + photons  low x not pos. without upgrades  parton kinematics ANfor inclusive hadrons AT in Interference-Fragmentation AT Collins FF in jets AN for back-to-back hadrons AN,T Ds, DY not possible without upgrades (muon trigger, FVTX + NCC helpful) Physics Goals determine first moment of the spin dependent gluon distribution, ∫01ΔG(x)dx. measurement of trans- versity quark distributions. Measurement of the Sivers distributions, Lz flavor separation of quark and anti-quark spin distri- butions Sivers Effect

    40. PHENIX Upgrade Components Muon from hadron decays Silicon barrel endcap Muon from W R1 charm/beauty & jets: displaced vertex R2 R3 Nosecone calorimeter g,g-jet,e,p0,h,c W and quarkonium: improved m-trigger rejection Muons from hadrons Muons from Ws pmuon

    41. Future Acceptance for Hard Probes NCC NCC MPC MPC VTX & FVTX EMCAL 0 f coverage 2p EMCAL -3 -2 -1 0 1 2 3 rapidity (i) p0 and prompt g with combination of all electromagnetic calorimeters (ii) heavy flavor with precision vertex tracking with silicon detectors (iii) combine (i)&(ii) for g-jet measurements

    42. First moment of ΔG(x) GS95 xDG(x) prompt photon Central arms • Measuring the Gluon Spin Contribution • to the Proton Spin: ΔG = ∫01ΔG(x)dx • Present measurements do not constrain functional form: They determine ΔG = ∫0.020.3ΔG(x)dx • Longitudinal double spin asymmetries for open charm with the FVTX measure ΔG(x), [0.001,0.3] • Longitudinal double spin asymmetries for direct photons with the NCC measure ΔG(x), [0.001,0.3]. Jet-photon measurements using the NCC constrain the quark gluon kinematics and are sensitive to the functional form of ΔG(x).

    43. Direct Photons (NCC) + Heavy Flavor (FVTX) NCC direct photons

    44. Nose Cone Calorimeter Q2 104 full 500 GeV Central arms prompt  NCC 500 GeV 103 NCC prompt  central 102 10 SMC SLAC/ HERMES 1 10-1 10-3 1 10-2 10-5 10-1 10-4 x log(xg) • NCC Spin physics … • Expands PHENIX’s kinematical coverage for jets, inclusive neutral pions, electrons, and photons to forward rapidity • Detection of both hadron jet and final state photon possible with the NCC and new silcon tracking detectors. • DG with NCC at low-x through jet-g, p0, e-m, open charm. • Isolation cut for W-bosons

    45. Probing lower-x with the NCC present NCC GS-C NCC prompt- Central Arm prompt- ALL ALL 150 pb-1 @ 500 GeV 70% Pol 150 pb-1 @ 500 GeV 70% Pol GS-B GS-A GS-C GS-C pT (GeV) pT (GeV)

    46. Spin structure of the quark sea Hermes: Phys.Rev.Lett 92 (2004) 012005 x Dd LO extraction from SIDIS x Dd • How does the spin gluon field “feed down” to the quark sea?  Gluons are polarized (G)  Sea quarks are polarized:

    47. Flavor separation of q and q sea Produced in pure V-A Quark helicities fixed AL • Inclusive single spin muon asymmetries (from W’s) is a good probe of Dq/q, Dq/q. • Complete theoretical treatment from first principles by Nadolsky and Yuan using re-summation and NLO techniques [NuclPhysB 666(2003) 31]. • Does not suffer from scale uncertainties pTm • W production • Produced in parity violating V-A process • Chirality / helicity of quarks defined • Couples to weak charge • Flavor almost fixed: flavor analysis possible • Experimentally clean measurement . • AL is parity violating → no false physics asymmetries. • Does not rely on knowledge of fragmentation functions Requires high luminosity 500GeV running + high rate muon trigger

    48. Complimentary measurements PHENIX vs HERMES SIDIS: large x-coverage uncertainties from knowing fragmentation functions W-physics: limited x-coverage High Q2 theoretically clean No FF-info needed

    49. Summary • RHIC is novel machine: provides collisions of polarized protons at high energies • High enough s  NLO pQCD is applicable • Strongly interacting probes can be used to study nucleon structure • PHENIX is well suited to the study of spin physics with a wide variety of probes. • Inclusive neutral pion data for ALL has reached statistical significance to constrain ΔG in a limited x-range (~0.02-0.3). • DG is consistent with zero in the measured region, but theoretical uncertainties are high. • Extending the x-coverage is crucial (higher/lower energy, upgrades) • DG is also being probed with charged pions, photons, etas, heavy flavor via muons and electrons, multi-particle “jets” … • Anti-quark helicity distribution via W decay • PHENIX has an upgrade program that will give us the triggers and vertex information that we need for precise future measurements of DG, Dq and new physics at higher luminosity and energy

    50. Brazil University of São Paulo, São Paulo China Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, Beijing Czech Charles University, Prague, Republic Czech Technical University, Prague, Czech Republic Academy of Sciences of the Czech Republic, Prague Finland University of Jyvaskyla, Jyvaskyla France LPC, University de Clermont-Ferrand, Clermont-Ferrand Dapnia, CEA Saclay, Gif-sur-Yvette IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau SUBATECH, Ecòle des Mines at Nantes, Nantes Germany University of Münster, Münster Hungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, Bombay Israel Weizmann Institute, Rehovot Japan Center for Nuclear Study, University of Tokyo, Tokyo Hiroshima University, Higashi-Hiroshima KEK, Institute for High Energy Physics, Tsukuba Kyoto University, Kyoto Nagasaki Institute of Applied Science, Nagasaki RIKEN, Institute for Physical and Chemical Research, Wako RIKEN-BNL Research Center, Upton, NY Rikkyo University, Toshima, Tokyo Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul Ewha Womans University, Seoul, Korea Kangnung National University, Kangnung Korea University, Seoul Myong Ji University, Yongin City System Electronics Laboratory, Seoul Nat. University, Seoul Yonsei University, Seoul Russia Institute of High Energy Physics, Protovino Joint Institute for Nuclear Research, Dubna Kurchatov Institute, Moscow PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg Lomonosoy Moscow State University, Moscow St. Petersburg State Technical University, St. Petersburg Sweden Lund University, Lund 14 Countries; 68 Institutions; 550 Participants USA Abilene Christian University, Abilene, TX Brookhaven National Laboratory, Upton, NY University of California - Riverside, Riverside, CA University of Colorado, Boulder, CO Columbia University, Nevis Laboratories, Irvington, NY Florida Institute of Technology, FL Florida State University, Tallahassee, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, IL Iowa State University and Ames Laboratory, Ames, IA Los Alamos National Laboratory, Los Alamos, NM Lawrence Livermore National Laboratory, Livermore, CA University of Maryland, College Park, MD University of Massachusetts, Amherst, MA Muhlenberg College, Allentown, PA University of New Mexico, Albuquerque, NM New Mexico State University, Las Cruces, NM Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TN University of Tennessee, Knoxville, TN Vanderbilt University, Nashville, TN