Spin of the proton and its transverse spin structure at RHIC

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Spin of the proton and its transverse spin structure at RHIC. HERMES seminar at Tokyo Tech November 9, 2005 Yuji Goto (RIKEN). RHIC – QCD collider. RHIC pC Polarimeters. Absolute Polarimeter (H  jet). BRAHMS & PP2PP. PHOBOS. Siberian Snakes. Siberian Snakes. PHENIX. STAR. - PowerPoint PPT Presentation

Text of Spin of the proton and its transverse spin structure at RHIC

  • Spin of the protonand its transverse spin structureat RHICHERMES seminar at Tokyo TechNovember 9, 2005Yuji Goto (RIKEN)

    Yuji Goto (RIKEN)

  • RHIC QCD collider

    Yuji Goto (RIKEN)

  • RHIC polarized-proton collisionLuminosity 11031 cm-2sec-1 at s = 200 GeV achieved81031 cm-2sec-1 at 200 GeV and 21032 cm-2sec-1 at 500 GeV in the futurePolarization 50% achieved 70% in the future

    Yuji Goto (RIKEN)

  • STAR and PHENIX STAR detector 2 coverage for jet measurement barrel TPC and EMC endcap EMC PHENIX detector limited acceptance high resolution central EMCal high-rate trigger and DAQ forward muon detectors

    Yuji Goto (RIKEN)

  • RHIC/PHENIX polarized-proton runs2005 First long longitudinal-spin polarized-proton runFigure of merit (LP4) more than 40 times larger thanthat of previous runs

    Yuji Goto (RIKEN)

  • Where is the proton spin ?Origin of the nucleon spin 1/2polarized DIS experiments showed the quark contribution is only 10-30%gluon contribution ?Scaling violation in polarized DIS

    Semi-inclusive DIShigh-pT hadron pairsopen charm productionB. Adeva et al., PRD 58, 112002 (1998).P.L. Anthony et al., PLB 493, 19 (2000).

    Yuji Goto (RIKEN)

  • Gluon contribution ?Polarized hadron collisionleading-order gluon measurement

    ALL of 0direct photon productionheavy-flavor productiongg + qg dominantsensitive to the gluon reaction

    Yuji Goto (RIKEN)

  • PHENIX ALL of 0* at input scale Q2 = 0.4 GeV- Run5 conclusively excludes GRSV maximal scenarios.- Data consistent with GRSV standard and GRSV G = 0.GRSV-max: g = 1.84

    GRSV-std: g = 0.42at Q2=1(GeV/c)2best fit to DIS data

    Theory modelC.L. (%)GRSV-std17.1-21.7*GRSV-max (Dg=g)0.0-0.0*GRSV Dg=016.7-18.4*GRSV Dg=g0.0-0.7

    Yuji Goto (RIKEN)

  • Single transverse-spin asymmetryLeft-right asymmetry

    Forward-rapidityFermilab-E704fixed-target experiment at s = 19.4 GeV

    Yuji Goto (RIKEN)

  • STAR forward pionRun2 resultsIn agreement with several models including different dynamics:Sivers: spin and k correlation in initial state (related to orbital angular momentum?)Collins: Transversity distribution function & spin-dependent fragmentation function suppressed? (hep-ph/0408356) Qiu and Sterman (initial-state) / Koike (final-state) twist-3 pQCD calculations

    Yuji Goto (RIKEN)

  • STAR forward pionRun3 resultsPositive AN at large positive xF has been confirmedLarger significance to be non-zero & positive than published dataThe first measurement of negative xF AN has been done, and is consistent with zeroSensitive to twist-3 gluon-gluon correlationStatistical error only for =4.1

    Yuji Goto (RIKEN)

  • STAR outlookDisentangling the dynamics of AN viaHigher precision AN measurement vs xF and pT AN with mid rapidity correlationForward jetProposal for forward calorimeter upgradeHeavy mesons and direct photons Low x gluons in nuclei Mid rapidity jetsDi-jet kT balance gluon Sivers functionInside jet particle correlation Collins function * Transversity

    Yuji Goto (RIKEN)

  • Mid-rapidity at PHENIXDifferent kinematic regionforward-rapidity at STAR (xF > 0.3)quark-gluon reaction dominantlarge contribution from x ~ 0.6 quark polarization/transversitymid-rapidity at PHENIX (xF ~ 0)contribution from both gluon-gluon and quark-gluon reactionsx = 0.03 0.1small quark polarization/transversityno gluon transversity in leading twistnegligible transversity & Collins effect contribution

    Yuji Goto (RIKEN)

  • Mid-rapidity at PHENIXRun2 resultsAN for both 0 and charged hadrons consistent with zero at mid-rapidity~5 times smaller asymmetry than STAR forward-rapidity data (~10%)comparable data with Fermilab-E704 for 0 and charged hadrons

    Yuji Goto (RIKEN)

  • Forward neutron asymmetryPHENIX local polarimeter R&D at IP12

    Yuji Goto (RIKEN)

  • Forward neutron asymmetryHadron CalEM CalAN = 0.1260.0080.041AN = 0.1160.0180.020preliminarypreliminarypreliminaryvery forward neutronAN ~ -12%xF > 0.2pT < 0.3 GeV/c

    Yuji Goto (RIKEN)

  • Local polarimeter at PHENIXLongitudinal component of the proton polarization at PHENIX410 GeV run in 2005analyzing power of local polarimeter roughly the same despite doubling of energy2005 run

    Yuji Goto (RIKEN)

  • Back-to-back jet at PHENIXBoer and Vogelsang find that this parton asymmetry will lead to an asymmetry in the distribution of back-to-back jetsShould also be able to see this effect with fragments of jets, and not just with fully reconstructed jetsBoer and Vogelsang, Phys.Rev.D69:094025,2004

    Yuji Goto (RIKEN)

  • Back-to-back jet at PHENIXMeasurement of the gluon Sivers function via AN for di-hadron angular correlationsSivers distribution is a transverse parton momentum distribution correlated with the nucleons spin axis, which could arise from orbital angular momentumError bars: Expected sensitivity with P=60% and 7 pb-1

    Yuji Goto (RIKEN)

  • Back-to-back jet at STAR

    Yuji Goto (RIKEN)

  • Spin dependence of kT of jetsPossible helicity effectWe may observe net effect (after averaging over impact factor)kT largerkT smallerSame helicityOpposite helicity

    Yuji Goto (RIKEN)

  • Spin dependence of kT of jetsRun3 result: hint of helicity dependence ?not yet sureRun5 data should yield a definite answer.

    Yuji Goto (RIKEN)

  • SummaryRHIC data began to provide restriction to the gluon-spin contribution to the proton spinWe need to know contribution of the orbital angular momentum as the final pieceRHIC has potential measurements of the orbital angular momentum and/or transverse spin structure of the protonsingle transverse-spin asymmetriesSivers effect/function measurementsWe will have some transverse-spin run in 2006

    Yuji Goto (RIKEN)

  • Backup slides

    Yuji Goto (RIKEN)

  • Naohitos analysis

    Yuji Goto (RIKEN)

  • Vertical vs radial run in 2006Boer and Vogelsang, PRD69:094025,2004STST1 = 01 = /21 = 0 :1 = /2 :private communication, Boer and Vogelsang

    Yuji Goto (RIKEN)

  • Spin dependence of kT of jetsBack-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 r introduces intrinsic kT in the initial state measurement of jet kT gives an access to parton orbital angular momentum

    Yuji Goto (RIKEN)

  • Transversity at PHENIXTransversity throught +- interference FFnon-vanishing support only in the mass region,

    Yuji Goto (RIKEN)

  • Transversity throught +- interference FFProjected asymmetrySmall aymmetry below5% but good rate! For 32pb-1 (1 week of running)5.2 Million events in 32 pb-115% with pair after cuts

    Yuji Goto (RIKEN)