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Spin Physics at RHIC-PHENIX

Spin Physics at RHIC-PHENIX. K.Okada Riken BNL research center. Contents. One of physics fields … Structure of nucleons RHIC accelerator PHENIX detector Analysis Result Outlook Summary. Structure of nucleons. What is inside the proton?. f(x,  2 ).

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Spin Physics at RHIC-PHENIX

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  1. Spin Physics at RHIC-PHENIX K.Okada Riken BNL research center K.Okada

  2. Contents • One of physics fields … Structure of nucleons • RHIC accelerator • PHENIX detector • Analysis • Result • Outlook • Summary K.Okada

  3. Structure of nucleons What is inside the proton? f(x,2) : depends on the energy scale, the evolution is known lepton Mainly from DIS measurement nucleon Q2 [GeV2] xf(x) x x K.Okada

  4. Structure of nucleons lepton beam  or  g*  or  nucleon target quark x△u(x) x△d(x) (Polarized) Polarized lepton, polarized nucleon x△u(x) x△d(x) x△s(x) Semi-inclusive DIS Where is gluon? x K.Okada

  5. Gluon polarization? Poor information from polarized DIS experiment Origin of the nucleon spin 1/2 ? Angular momentum gluon quark DS ~0.25, Dg, DL unknown K.Okada

  6. Gluon polarization? Dg2 DgDq Dq2 How to measure Dg: p0 Hard Scattering Process Polarized hadronic collisions ++: cross section in   +-: in   Any interaction related to gluon can be a probe (0 , Jet, h±, Direct , J/psi, charm…) Gluon interaction in the first order. High energy to apply the perturbative QCD. K.Okada

  7. Relativistic Heavy Ion Collider K.Okada

  8. Relativistic Heavy Ion Collider K.Okada

  9. RHIC PHENIX experiment • Relativistic Heavey Ion Collider (for QGP) • and the first collider of polarized proton Proton source Ion source K.Okada

  10. Key features of RHIC +-+-+- --++--++ Keep the polarization during the acceleration. Several techniques (Siberian snake etc.) Different helicity configuration in every 106ns. (Cancellation of the detector effect in the asymmetry) Polarimetry (Hiromi’s ph.D thesis) K.Okada

  11. H-jet measures beam polarization at RHIC Vol 45, number 8 638 (2006) 450 K.Okada

  12. PHENIX detector proton proton Central arms + Forward muon arms K.Okada

  13. PHENIX central arm trigger —Requirement: (s=200GeV) 2006 vertex cut (~0.5) Collision trigger (~0.5) ~200kHz collision rate 5kHz (Data acquisition limit) Rejection power ~100 —EMCal and RICH trigger K.Okada

  14. Concept of EMCal-RICH trigger EMCal EMCal RICH RICH h PHENIX central arm 2 types of EMCal (PbSc, PbGl) (0) (Ring Image Cherenkov detector) (0) : EMCal Electron : EMCal and RICH High energy hadron : EMCal (through hadronic interactions) and RICH K.Okada

  15. EMCal turn-on curve is important Distribution of the highest cluster energy in a event from run3 pp data. Important for RP! E[GeV] E[GeV] Because of the steep falling distribution of the maximum energy in a event, The rejection power is determined by the lower tail. PMT gain variation + Trigger tile variation I established a procedure to reduce these variations. Now two terms are comparable. K.Okada

  16. Rejection Power Improvements Old RP New RP The threshold resolution improvement resulted in the rejection power (RP) increase. Rejection power of 4x4 triggers improved for more than 2 times. K.Okada

  17. PHENIX polarized-proton runs Longitudinally Polarized Runs Transversely Polarized Runs ** Not yet finalized K.Okada

  18. Analysis (briefly) 1<p<2GeV 3<p<4GeV 8<p<9GeV Example : 0 EMCal Calibration MIP electron E/p Mgg pi0 peak position Invariant mass of 2 photons At first, we need to confirm the theory baseline  Cross section measurement Luminosity Beam current, size Trigger rate K.Okada

  19. 0cross section at 200GeV p0 Dg2 DgDq Dq2 T Run2: PRL91,241803(2003) NLO pQCD calculations are consistent with cross-section measurements K.Okada

  20. ALL of 0 at Ös=200GeV • p0 ALL vs. pT from Run6 Filtered data compared with Run5 Preliminary photon triggered data as well as Run5 Minimum bias below 1 GeV • Run-6 Data set from 2.0-2.7 times improvement on statistical uncertainties from Run5. • Lower pT Run-6 points will come with full production K.Okada

  21. ALL of 0 at Ös=200GeV g = 1.84 g = 0.42 at Q2=1(GeV/c)2 best fit to DIS data • Run-6 Data set from 2.0-2.7 times improvement on statistical uncertainties from Run5. • Lower pT Run-6 points will come with full production • Run5 data not consistent GRSV-max in this x-range. • Run6 sufficient to differentiate GRV-std from Dg=0 K.Okada

  22. Determination of g A global analysys (PHENIX+ other experimental data) For examplehep-ph/0603213 (Hirai et. al) Type 2 : JLab, HERMES, COMPASS Type 1: Type 2+ PHENIX 0 K.Okada

  23. Prompt g production at Ös=200GeV g Gluon Compton Dominates • At LO no fragmentation function • Small contamination from annihilation DgDq DqDq Run 3 hep-ex/0609031 K.Okada

  24. Other reactions (central arm) Yield (Arbitrary unit) pT[GeV/c] 0 until merging  in high pT ± low trigger eff.  Clean but needs luminosity Reminder: any reaction contains gluon brings the information. In PHENIX 0 P N :Beam polarization :Yield K.Okada

  25. Other observables related to spin —ALL (difference of +  and +） gluon polarization etc. 0, ±,Direct ,Jet, J/psi, open charm Jet correlation —AN (left-right asymmetry in +• ） Asymmetry in forward region (E704, STAR, BRAHMS) At PHENIX Asymmetry in Very forward neutron Zero in 0,h±production in the central region. Both experiment and theory are developing. It might be interesting. —AL ( Difference of +• and +•） Parity violating mode (=weak interaction) Difference between flavors Need high luminosity for W production. — Spin transfer (correlation between beam state and final state）  etc. — ATT (difference of + and +） K.Okada

  26. Outlook Spin Plan Report BNL-73798-2005 Charm, Beauty With silicon VTX K.Okada

  27. Detector upgrade (PHENIX-SPIN) — Silicon VTX detector Charm, Beauty detection Kinematics — Forward calorimeters （MPC, nose-cone) Transverse spin physics Kinematics —Forward muon trigger upgrade W physics K.Okada

  28. Summary •RHIC-PHENIXstatus —ALL ( difference between +  and　+）　: gluon spin Results of 0 (the highest statistics) (The gluon polarization is low.) —AN ( left-right asymmetry in +• ） The asymmetry is observed at RHIC energy in the forward region. Relatively new field in both theory and experiment. •Future Settle the issue of gluon polarization Possibility of AN physics Flavor separation with W production K.Okada

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