1 / 32

Current status of RHIC Spin Program

Current status of RHIC Spin Program. Workshop on Hadron Structure at J-PARC Nov. 30, 2005 Kiyoshi Tanida (RIKEN/RBRC). Outline. Overview of the RHIC spin project Recent spin physics results Cross section measurements A LL measurements A N measurements Other measurements

clayton-bryan
Télécharger la présentation

Current status of RHIC Spin Program

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Current status of RHIC Spin Program Workshop on Hadron Structure at J-PARC Nov. 30, 2005 Kiyoshi Tanida (RIKEN/RBRC)

  2. Outline • Overview of the RHIC spin project • Recent spin physics results • Cross section measurements • ALL measurements • AN measurements • Other measurements • Future prospects • Summary

  3. s ++ - s +- ( ) ( ) = s ++ + s +- ( ) ( ) Overview of the RHIC spin project • Main Physics Study of spin structure of proton1/2 = 1/2DS + DG + L (DS ~ 0.25) • How to study? ALL -- double spin asymmetry in pp collision = (parton pol.)2× (aLL in parton reaction)

  4. Examples of reaction channels • Direct photon: g + q  g + q- ~10% contribution from other processes (e.g.`qq  gg) golden channel for gluon polarization- Need high luminosity (> 100 pb-1). • Jet, high-pT hadron production- mix of various processes, q+q, g+g, g+q, ...- feasible at relatively small luminosity (~pb-1) • Heavy flavor • W -- spin-flavor structure

  5. Brhams pp2pp PHENIX STAR The Relativistic Heavy Ion Collider accelerator complex at Brookhaven National Laboratory

  6. RHIC p+p accelerator complex The polarimeters are experimental devices RHIC pC “CNI” polarimeters absolute pH polarimeter BRAHMS & PP2PP PHOBOS RHIC Siberian Snakes PHENIX STAR Siberian Snakes Spin Rotators 5% Snake LINAC BOOSTER AGS pC “CNI” polarimeter Pol. Proton Source AGS Coulomb-Nuclear Interference 200 MeV polarimeter Rf Dipoles 20% Snake

  7. AN for Carbon polarimeters @RHIC scattered proton (polarized) proton beam “Analyzing power” or transverse single-spin asymmetry polarized proton target or Carbon target recoil proton or Carbon this exp E704 @ FNAL preliminary AN for proton

  8. RHIC pp performance Projection RHIC/AGS User meeting 2005 BNL, Upton, NY 11973

  9. s = 200 GeV P recorded L recorded LP4 data volume 2001-2002 transverse-spin run 15% 0.15 pb-1 20 TB first polarized proton collisions 2003 longitudinal-spin run 27% 0.35 pb-1 1.5 nb-1 35 TB spin rotators commissioned, AGS p-C CNI polarimeter 2004 commissioning run (longitudinal spin) 40% 0.12 pb-1 3.3 nb-1 AGS warm snake commissioned, gas-jet absolute polarimeter 2005 longitudinal-spin run (w/ short transeverse run) 49.5/44.5% 3.8 pb-1 205 nb-1 262 TB AGS cold snake installed Statistics @PHENIX 2005 – First long longitudinal-spin polarized-proton run Figure of merit (LP4) more than 40 times larger than that of previous runs

  10. Recent spin physics results • Cross sections(not exactly spin, but important cross-check for data/theory reliability) • PHENIXp0 and direct photon • STARinclusive jet production,forward p0 • Brahms, p± • All agree well withNLO pQCD calculation

  11. ALL measurements Currently available results: • PHENIX • midrapidity: p0, "jet" (multi-particle) • forward rapidity: J/Y • STAR • midrapidity: jet In (near) future • charged hadrons, h,direct photon, heavy quarks,...

  12. p0 ALL -- PHENIX ¨ GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775. * At input scale: Q2 = .4 Gev

  13. Inclusive jet -- STAR RUN3+4 data Results limited by statistical precision Total systematic uncertainty ~0.01 (STAR) + beam pol. (RHIC)

  14. ALL for “jet” -- PHENIX • Jet detection -- Tag one photon, sum observedenergy/momentum nearby (R < 0.3) • Jet pT estimated by simulations (modified PYTHIA) Run3 data only (Run5 data is under analysis)

  15. J/y ALL J/y: produced via almost pure gluon fusion Will be sensitive to gluon polarization, now statistically limited.

  16. AN measurements • Brahms • forward/backward charged pion, proton • pp2pp • AN in pp elastic scattering • STAR • forward p0 • inclusive forward particles • midrapidity charged particles • PHENIX • midrapidity: charged particles, p0 • very forward neutrons

  17. forward p± -- Brahms BRAHMS preliminary 2 < h < 5.2 AN for negative xF are consistent with 0 protons: AN ~0 • Signs are consistent with lower energy results • Twist-3 model can explain the result (flat xF distribution, lower AN for higher pT)

  18. Forward p0 -- STAR • Preliminary pT dependence • was obtained • xF>0.4, h ~ 4 • C/pT fit gives C = 0.07±0.01 • @1 GeV/c • Comparison with theoretical calculation may constrain Sivers function

  19. AN in pp2pp AN • pp elastic scattering • ~1s deviation from CNI curve -- interference of hadronic “non-flip” + electromagnetic “spin-flip” • Other contributions, e.g. Reggeon or Pomeron exchange exist? s1/2=200 GeV -t (GeV/c)2

  20. AN of very forward neutron --PHENIX LocalPol ～1800cm PHENIX Collision Point 10cm blue beam yellow beam ±2mrad Dx magnet <AN>=-0.1100.015 @ s1/2=200 GeV very forward: pT ~ 0.1 GeV/c almost no xF dependence Mechanism unknown

  21. AN persists at sqrt(s) = 410 GeV yellow backward blue forward raw asymmetry yellow forward blue backward

  22. Other spin results • I can't show all of them (e.g., Λ spin transfer) • Spin dependence of transverse momentum of jets • Back-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× rintroduces intrinsic kT in the initial state  measurement of jet kT gives an access to parton orbital angular momentum

  23. possible helicity effect larger kT smaller kT Same helicity Opposite helicity We may observe net effect (after averaging over impact factor)

  24. p+p s = 200 GeV 1.5<pT<2.0 Fit = const + Gauss(0)+Gauss() 3.0<pT<4.0  kT Measurement in PHENIX o - h correlation functions in f distribution d+Au Intra-jet pairs angular width : N jT ... fragmentation Inter-jet pairs angular width : F jT  kT ... fragmentation + kT

  25. Helicity Dependence Stat. only Hint of Helicity dependence?  not yet sure Run05 data should yield a definite answer. BS variance (stat. + syst.)

  26. Future prospects • Budget situation for Run6 is very hard, but ... • We are going to accumulate > 100 pb-1 with P > 70% at s1/2=200 GeV by 2009. • Then switch to s1/2=500 GeV  Determination of Dg(x) with many channels including direct photon • Other physics (no time to discuss...) • Detector upgrades are ongoing • STAR: Forward meson detector, trigger/DAQ, ... • PHENIX: Si-VTX detector, W trigger upgrade, ...

  27. Jet ALL from STAR Run 5 Will be able to distinguish Dg=0 and g inputs

  28. ALL from PHENIX Run 5 Direct photon Jet ALL h, electron, m, L, ...

  29. ALL of direct photon • “Golden Channel” for Dg, high luminosity required • s = 200 GeV until 2009 • s = 500 GeV from 2009 GRSV-max (Dg=g) GRSV-std

  30. 2 0 h AN of Jet kT(Run 6 and beyond) • A probe to access to Sivers functions. Boer and Vogelsang, PRD69:094025,2004 STAR projection

  31. Summary • RHIC-spin has taken first long longitudinal-spin polarized-proton collision data in Run5 • Preliminary results from Run 5 are available • ALL data from PHENIX and STAR have significant impact on the gluon spin contribution in the proton • Dg=g scenario is excluded • Many data on AN in various channels and other measurables -- interesting physics case • More data will come -- promising.

More Related