PHENIX Spin Program Recent results A.Bazilevsky Brookhaven National Laboratory for the PHENIX Collaboration XXXXth Rencontres de Moriond - March 12-19, 2005 QCD and Hadronic interactions at high energy

Proton Spin Structure Spin Quark SpinGluon Spin Orbital Angular Momentum  Polarized DIS: contribution of quarks to proton spin is amazingly small  0.25  Main candidate to carry proton spin - Gluons Gluon polarization (  G) remains poorly constrained   G measurements – main RHIC-Spin goal

Polarised PDF A symmetry A nalysis C ollaboration M. Hirai, S. Kumano and N. Saito, PRD (2004) Valence Dist’s are determined well Sea Distribution poorly constrained Gluon can be either pos, 0, neg!

PHENIX Spin Program Prompt Photon  Production Heavy Flavors Utilizing high energy polarized proton beams of RHIC

RHIC as polarized proton collider BRAHMS & PP2PP (p) STAR (p) PHENIX (p) AGS LINAC BOOSTER Pol. Proton Source 500  A, 300  s Spin Rotators Partial Siberian Snake Siberian Snakes 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipoles RHIC pC Polarimeters Absolute Polarimeter (H jet) 2  Pol. Protons / Bunch  = 20  mm mrad RHIC accelerates heavy ions to 100 GeV/A and polarized protons to 250 GeV

Spin Running at RHIC-PHENIX Run2: –Transversely polarized p+p collisions –Average polarization of ~15% –Integrated luminosity 0.15 pb -1 Run3: 2003 –Longitudinally polarized p+p collisions achieved –Average polarization of ~27% –Integrated luminosity 0.35 pb -1 Run4: 2004 –Longitudinally polarized p+p collisions –Polarization of ~40-45% –Integrated luminosity 0.15 pb -1 Run5: starting next month –Expected Longitudinally polarized p+p collisions –Expected P ~ 50% –Expected L > 10 pb -1

 0 Cross Section in pp at  s=200 GeV 9.6% normalization error not shown Phys. Rev. Lett. 91, (2003)  NLO pQCD consistent with data within theoretical uncertainties PDF: CTEQ5M Fragmentation functions: Kniehl-Kramer-Potter (KKP)Kniehl-Kramer-Potter (KKP) Kretzer Spectrum constrains D(gluon  ) fragmentation function  Important confirmation that pQCD can be used to extract spin dependent pdf’s. Same comparison fails at lower energies |  |<0.35

 0 A LL Preliminary PRL 93,  0 A LL small (or consistent with zero) (P) Polarization (R) Relative Luminosity (N) Number of pi0s

 0 A LL :  G constrain Fractional contribution to pp  0 X at  s=200 GeV at mid-rapidity  0 production at low/moderate pT’s is sensitive to gluon distribution

 0 A LL :  G constrain  Note considerable contribution of soft physics in the lowest p T point (  50%) Comparison with theory: GRSV-std 21-24% (p T >1 GeV/c) 27-29% (p T >2 GeV/c) GRSV-max % (p T >1 GeV/c) % (p T >2 GeV/c) Run3+4 Consistent with GRSV-std Less consistent with GRSV-max B.Jager et al., PRD67, (2003) This is the first constrain of gluon polarization using strongly interacting probes; the current sensitivity is comparable to the world set of polarized DIS data

Prompt photons and  G NLO pQCD describes data well  can be used to interpret A LL (  ) A LL (  ) needs large luminosity: results expected in Gluon Compton Dominates –At LO no fragmentation function –Small (  15%) contamination from annihilation pol-DIS theory Unpol. cross section |  |<0.35

Transverse Single-Spin Asymmetries Observed in  0 production at forward region (E704, STAR) –Increase with x F Origin of A N –Transversity  Spin-dep fragmentation (Collins effect) –Intrinsic-k T imbalance (Sivers effect) –Higher-twist effects –Or combination of above left right A N at mid-rapidity (|  |<0.35) A N for both charged hadrons and neutral pions consistent with zero.

Future 2009  10:  q-bar from W  A L 2005  07:  G from  0 A LL 2007  08:  G from  A LL

Summary RHIC has been successful as the world’s first polarized proton collider, opening up new kinematic regions for investigating the spin of the proton The first spin results from PHENIX are out and stimulating discussion within the theoretical community –A N of neutral pions and non-identified charged hadrons –A LL of neutral pions Many more years of exciting data and results to look forward to! Spin physics at PHENIX planned for 2005 and beyond –Measure gluon polarization via direct photon double longitudinal asymmetry –Probe gluon polarization from heavy flavor production (gg fusion) via electrons –Probe polarization of sea quarks via W boson single longitudinal asymmetry

Backup slides

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 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 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 Brazil University of São Paulo, São Paulo China Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, Beijing 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 University of Tokyo, Bunkyo-ku, Tokyo Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul 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 St. Petersburg State Technical University, St. Petersburg Sweden Lund University, Lund 12 Countries; 57 Institutions; 460 Participants

PHENIX Detector Central Arms: |  |<0.35,  =2  90 0 Charged particle ID and tracking; photon ID Muon Arm: 1.2<|  |<2.4 Muon ID and tracking Global Detectors Collision trigger Collision vertex characterization Relative luminosity Local Polarimetry Philosophy: High rate capability & granularity Good mass resolution and particle ID  Sacrifice acceptance

 G: other experiments GRSV-max GRSV-std HERMES SMC PHENIX x-range  Theory curves from W.Vogelsang  HERMES: high pt hadron pairs (PRL84, 2584, 2000) Consistent with both GRSV- max and GRSV-std  SMC: high pt hadron pairs (hep-ex/ ) Consistent with GRSV-std  PHENIX:  0 A LL Consistent with GRSV-std So far all results are consistent with GRSV-std

 G: Prompt Photons A LL Statistics with full design luminosity and polarization (  Ldt=320 pb -1, P=70% ) prompt photon GS95 xGxG x GRSV: Frixione and Vogelsang, Nucl. Phys. B568:60 (2000) GS95: Gehrmann and Stirling, PRD53, 6100 (1996)

ANAN PRL 92 (2004) E704

 G: Heavy Flavor Provides more independent  G measurements in PHENIX »Helps control experimental and theoretical systematic errors »Different channels cover different kinematic regions bb  e  X direct  cc  eX H. Sato Decay channels: »e + e -,  +  -, e , e, , eD,  D Open heavy flavor production

Flavor Decomposition Drell-Yan production of lepton pairs –Maximal parton level asymmetry: a LL = -1 –Possible severe background from semi-leptonic decays of open charm productions W production »Produced in parity violating V-A process — Chirality / helicity of quarks defined »Couples to weak charge — Flavor almost fixed: flavor analysis possible — Flavor ID reduces uncertainty in current pol-PDF models. »PHENIX-Muon Arms

W Production x 1 >>x 2 : A L (W + ) →  u/u(x 1 ) _ x 2 >>x 1 : A L (W + ) → -  d/d(x 1 ) W Z 800 pb -1 W dominates for muon p T >20 GeV/c quark x from parton kinematics

PHENIX Local Polarimeter SMD Forward neutron transverse asymmetry (A N ) measurements SMD (position) + ZDC (energy) ZDC Vertical   ~  /2 Radial   ~ 0 Longitudinal  no asymmetry  distribution

Neutron Asymmetry »Unexpectedly large asymmetry found »EMCal & ZDC results are consistent Y. Fukao

Upgrades Muon Trigger for W Bosons Measure sea quark polarization Nose Cone Calorimeter  + jet   G, extends x-range Silicon Vertex Tracker heavy flavor and jet reconstruction

Silicon Vertex Detector 13cm 20cm Barrel: Two layers of pixels (2.5, 5cm) Two layers of strips (~10, 14cm) Endcap: Four sets of mini-strip lampshades

Physics with Silicon VTX Jet-axis for photon+jet-axis  constraint on x c  e,  displaced vertex low-x S/B, D  K  high-x b  displaced J/  low/high-x, b  e, displaced vertex high -x