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The pursuit of polarized gluon distribution in the nucleon with PHENIX

The pursuit of polarized gluon distribution in the nucleon with PHENIX. Abhay Deshpande State University of New York at Stony Brook Riken BNL Research Center October 10, 2005. Overview. Relevance of polarized gluon distribution in the “nucleon spin puzzle”

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The pursuit of polarized gluon distribution in the nucleon with PHENIX

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  1. The pursuit of polarized gluon distribution in the nucleon with PHENIX Abhay Deshpande State University of New York at Stony Brook Riken BNL Research Center October 10, 2005

  2. Overview • Relevance of polarized gluon distribution in the “nucleon spin puzzle” • PHENIX Spin measurements towards understanding the spin puzzle • ALL(p0) from Run-3 & Run-4 : a quick reminder • RHIC Run-5 and expectation from PHENIX • Run-6 and beyond • Putting all data in perspective: a new initiative on combining world’s spin data Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  3. Gluon Contribution to Nucleon Spin is Unknown • SMC, PRD58, 112002 (1998) • NLO pQCD analysis of fixed target DIS data: (CERN, SLAC, DESY) • Quark contribution to nucleon spin well constrained but gluon contribution has huge uncertainties • Since then many other analyses have been published with qualitatively identical results (E143 Collaboration, AAC Collaboration, E. Leader et al.) • New techniques to get to gluon spin necessary:RHIC Spin ideal, also explores new kinematics Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  4. Polarized Gluon Measurements with PHENIX • Many channels involving polarized gluons in the initial state of scattering: • Allow independent constraints on the measurement • Have different experimental systematic uncertainties • Measurements with PHENIX detector • Inclusive neutral and charged pion production • 2003-2005/6 • Inclusive prompt photon production (details in K. Okada’s talk) • 2005-2008/9 • Future upgrade (Si VTX TRK: A. Taketani) will allow additional measurements of gluon distribution using g-jet production, heavy quark production …. etc. • Beyond 2009 mostly in the 500 GeV CM program • Extend the kinematic range to lower x Large Cross Sections Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  5. s(pp p0 X): Corner stone of RHIC measurements • A well understood process: cross sections calculable in NLO pQCD in mid & high rapidity high rapidity mid rapidity Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  6. p0 production and partonic contributions • Fractional contribution of • partonic scattering to total • neutral pion production • Gluon interactions dominate • the low pT region • In th every low pT (< 3 GeV) • gg process dominates. • Asymmetry insensitive • to the sign of gluon • distribution • Needs measusurement at • high pT (5-10 GeV) • where qg process • important & • Measurements of • charged pions (see later) gg + qg scattering dominant Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  7. PHENIX Run 3+4 vs. Gluon Parameterizations • GRSV-std: best fit to DIS data • GRVS-max • Data prefers the GRSV-std curve (and hence the gluon distribution and its first moment) • B. De Jaeger et al. Phys. Rev. D67, 0504005 (2003) Data seem to prefer low value of DG? C2 probability 24% for GRSV-std and 3% for GRSV-max GRSV-std corresponds to DG = 0.5 at Q2 = 1 GeV2 while GRSV-max corresponds to about 1.8 at the same scale. B. De Jaeger et al, Phys. Rev. D67, 0504005 (2003) Need to improve this measurement ASAP! Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  8. Run-5 pp: March 05 - June 05 • CAD hardware upgrades: Cold Siberian Snake in AGS commissioning, significantly increased NEG coated beam pipes…. • Highlights of RHIC accelerator performance: • Average ~47-50% beam polarization (routinely available) • Number of bunches in each ring 56 (beginning) --> 110 (towards the end) • Delivered luminosity 12.8 pb-1 in ~11 weeks of operation • Acceleration of polarized protons to 205 GeV/c, success demonstrated by (transverse orientation at the experiments) • Measured asymmetry by RHIC CNI polarimeters • PHENIX confirmed observation of forward neutron asymmetry • PHENIX took its largest single sample of polarized pp data • 260 TB data, with various trigger setups • ~3.8 pb-1 of longitudinal double spin collisions, 0.16 pb-1 of transverse spin collisions, • All data transferred to CCJ almost in real time for production 3.8 pb-1 at 48% polarization corresponds to 205 nb-1 in Figure of Merit ~40 times better than 2003+2004! Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  9. Run-5 Neutral Pion Asymmetry Analysis status and prospects • Relative luminosity studies [K. Boyle(SBU)]: Interesting new effects observed: • First tests/trials with increased number of bunches in fills by CAD, studied and mostly understood • Expect no major show stoppers, relative luminosity uncertainty presently estimated to be the same as in the previous years • Detector (EMCal, TOF) efficiency studies [Y. Fukao (Kyoto/RIKEN), K. Nakano (Tokyo/RIKEN)] -- DONE • Local Polarimetry studies done [M. Togawa (Kyoto)] -- DONE • Beam polarization in Run-5 using online values • Preliminary values expected (soon) • Significant improvement in beam polarization uncertainty expected • ALL(p0) Run-5 Result expected to be released at PANIC’05 • Kieran Boyle and Yoshi Fukao to present the results in a parallel session Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  10. Scaled from Run3 by Y. Fukao 4/pb Run-5 Neutral Pion Asymmetry • GRSV std corresponds to a very small polarized gluon integral • DG ~ 0.5 at Q2=1 GeV2 • While Run 3+4 seem only to rule out GRSV-max parameterization, Run 5 data will allow us to get the first definitive estimate for the magnitude of the first moment of the polarized gluon distribution in the probed kinematic region Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  11. M. Stratmann et al. Charged pion asymmetries: Sign of DG? • Run-5 neutral pion & charged pion asymmetries will start to resolve the sign of the DG as well! Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  12. Plans for Run-6 & Beyond • Many other efforts underway for DG measurements in the near future: • Neutral pions result consolidation + charged pion asymmetries • Direct photon (see K. Okada’s talk) • ALL of Jet-like cluster: Jet surrogates in PHENIX! (K. Nakano, APS/DNP) Run-3 • By 2009 we expect ~90 pb-1 luminosity in PHENIX at 200 GeV CM accumulated in 35 weeks of pp running • Completion of 200 GeV CM program • Si VTX TRK will be available at this time and the 500 GeV program begins • DG with g-jet coincidence • DG with heavy quark production Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  13. Global Analysis of Polarized Scattering Data : A new initiative • We must extract the maximum information out of the existing and anticipated data (including the polarized DIS and RHIC pp) • Require: “A Global Analysis” of all available data using the state-of-the-art theoretical formulism and tools • Emphasis: Careful evaluation of experimental and theoretical uncertainties and their correlations • General method clear & obvious, details of including pp at NLO complicated, but W. Vogelsang & M. Stratmann have developed early ideas • A new initiative is being considered with RHIC experimentalists, theorists & members of CTEQ collaboration: • CTEQ willing to provide the tools & advice in such an analysis • BNL/Stony Brook theory & other CTEQ colleagues are willing to help with spin related theoretical/technical issues • Some of us will start this shortly across collaborations with an aim to develop this as the 200 GeV RHIC Spin program ramps up Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  14. Concluding Thoughts • These are exciting times for “RHIC Spin”! • First conclusive results on DG from RHIC may be just around the corner • Neutral pion production has paved the way and charged pion & direct photon analyses will follow • Intermediate term outlook is exciting due to the anticipation of a huge amount of RHIC polarized pp data • Utilizing these data in the most comprehensive way to extract maximum information on polarized gluon distribution is essential & will require the a CTEQ/MRST like effort. This is about to start. Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  15. Backup slides PHENIX data transfer, production and Spin Fest (2 slides) Relative luminosity studies: number of bunches 56-->120 variation in bunch population early part, later part & bbll1 vs. zdcll1 (both narrow correlations) (2 slides)

  16. The Data Transfer & Production at CCJ Data transfer between RCF and CCJ: data sample: 260 TB rate : 60MB/sec. duration : ~11 weeks RIKEN/CCJ: Yasuhi Watanabe, Satoshi Yokkaichi, Takashi Ichihara PHENIX : Martin Purschke, Mickey Chiu, Hiro Hiejima RCF : Dantong Yu, Shigeki Misawa, Terry Healy, Razvan Popescu, John Riordan • Production at CCJ • Led by Hisayuki Torii • Just finished! • Data analysis underway http://www.cerncourier.com/main/article/45/7/15 3-4 TB/day Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  17. Spin Fest’05 at RIKEN: July-August’05 Aims and aspirations: • Start analysis effort: not just Run-5 but make a basis for an coherent analysis group effort for all future runs • Support production effort if needed • Introduce PHENIX analysis and spin issues to the new comers (of which there are many) • Weekly seminars by PHENIX detector and analysis specialists • A week long SPIN QCD summer school (Stratmann, Kumano, Sudoh) • Run on a “run schedule”: period coordinators for 2 weeks, scientific advisors visiting RIKEN for short periods, over all Analysis coordination: Yuji Got, Kiyoshi Tanida, and AD • Successful in “Jump starting” many physics analyses: the fruits of which will be available starting this fall… well in to the future! Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  18. Relative Luminosity Studies Run-5 Two methods used by CAD to increase RHIC pp luminosity: • More protons per bunch (limited by electron gas production effects) improved by NEG coating of beam pipes (85% complete in Run-6) • Increase number of bunches in RHIC rings from 56--> 110 • Number of interesting effects observed w.r.t. relative luminosity • Now understood • Final relative luminosity uncertainty similar to Run-3/4 values Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

  19. Relative Luminosity Studies Run-5 • Two methods used by CAD to increase RHIC pp luminosity: • More protons per bunch (limited by electron gas production effects) improved by NEG coating of beam pipes (85% complete in Run-6) • Increase number of bunches in RHIC rings from 56--> 110 • Number of interesting effects observed w.r.t. relative luminosity, although mostl are now understood Gluon Spin Investigations: A. Deshpande (SBU/RBRC)

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