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RHIC Spin Physics

RHIC Spin Physics. M. Grosse Perdekamp University of Illinois and RBRC. STAR. Physics goals Experimental tools Polarized proton-proton collisions at high energies Results and outlook Gluon Spin Transverse spin physics W-physics and upgrades.

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RHIC Spin Physics

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  1. RHIC Spin Physics M. Grosse Perdekamp University of Illinois and RBRC STAR • Physics goals • Experimental tools • Polarized proton-proton collisions at high energies • Results and outlook • Gluon Spin • Transverse spin physics • W-physics and upgrades International Workshop on Deep Inelastic Scattering,April 20-24, 2006 ,Tsukuba, Japan

  2. RHIC  five complementary experiments RHIC: ion-ion and polarized p-p Collider pp2pp RHIC Spin Overview

  3. Physics at the Relativistic Heavy Ion Collider • Quark Matter at high Temperatures and Densities • ion-ion collisions (Cu-Cu, Au-Au: √sNN=22.5, 62, 130, 200 GeV) • Proton Spin Structure • polarized proton-proton collisions (p-p: √s=200 to 500 GeV) • Low-x and high parton densities • ion-deuteron collisions (d-Au: √sNN=200 GeV) C. Cagliardi low-x: Sat.11.10 very active field: eg. 74 PRL letters in the first 5 years RHIC Spin Overview

  4. Proton Spin Structure in Polarized p-p Collisions at RHIC goals determine first moment of the spin dependent gluon distribution. flavor separation of quark and anti-quark spin distributions measurement of trans- versity and Sivers distributions available channels jets, hadrons, photons, photon-jet, heavy flavor Single spin lepton asym- metries in W-production (1) AN (2) ATT in Collins- and Interference-Fragmentation (3) ATT and AT In Drell Yan RHIC Spin Overview

  5. Access to Parton Distributions at RHIC Measure: (spin dependent) cross sections QCD analysis: (spin dependent) distribution functions RHIC Spin Overview

  6. Example: DG(x) from a global NLO pQCD analysis with projected future direct photon data from PHENIX Does NLO pQCD provide a reliable framework for the interpretation of polarized proton data in terms of polarized parton distribution functions? QCD analysis of inclusive DIS data QCD analysis DIS data + future direct photons M. Hirai, H.Kobayashi, M. Miyama et al. (Asymmetry Analysis Collaboration) RHIC Spin Overview

  7. Inclusive Hadron Cross Sections vs NLO QCD PHENIX π0 cross section a |η|<0.35 Phys.Rev.Lett.91:241803,2003 STAR π0 cross section a 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 RHIC Spin Overview

  8. Direct Photons and Inclusive Jets vs NLO pQCD Direct Photon Cross section Inclusive Jet Cross section M.Miller, hadronic final states: Sat.14.20 PHENIX Preliminary Good agreement between NLO pQCD calculations and experiment at RHIC !  Use NLO pQCD analysis to extract (spin dependent) quark and gluon distributions from RHIC data! Theory calculation show good agreement with the experimental cross section. STAR Preliminary M. Stratmann, spin: Fr 16:30 Theory perspective: RHIC Spin Overview

  9. Last Week at RHIC peak average  design L 2.5 1.2 6.0 P 67% 61% 70% Luminosity in 1031cm-2s-1 A novel experimental method: Probing Proton Spin Structure Through High Energy Polarized p-p Collisions RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes A. Bravar, spin: Fr 16:10 BRAHMS & PP2PP PHOBOS 2005 Complete! high current polarized source high energy proton polarimetry helical dipoles magnets Siberian Snakes Spin Flipper PHENIX STAR Spin Rotators Partial Snake Strong Snake Helical Partial Snake Polarized Source LINAC AGS BOOSTER 200 MeV Polarimeter Generous support from RIKEN, Japan and DOE Rf Dipole AGS Polarimeter RHIC Spin Overview

  10. Polarized p-p at RHIC: Detector Instrumentation • Upgrades to adapt “heavy ion detectors” for high rate p-p • environment (eg. PHENIX trigger, STAR EMC, • STAR tracking at high momentum) • Local polarimeters to verify polarization direction at the • interaction point (important for longitudinal spin!) • Relative luminosity: arises in calculating asymmetries • between yields from different bunch crossings, say i and j eg. F. Simon, spin: Sa10:20 RHIC Spin Overview

  11. BRAHMS: AN for charged π,K, p 100% transverse spin! Two spectrometer arms with good particle ID at high momenta RHIC Spin Overview

  12. PHENIX spin physics program: ∆G, ∆q/∆q, Sivers, δq EM Calorimeter Beam-Beam Counter Time Expansion Chamber Muon Tracking Chambers Central Arms Muon ID Panels Pad Chambers Multiplicity/Vertex Detector North Muon Arm Drift Chambers South Muon Arm Time of Flight Panels Four spectrometer arms with excellent trigger and DAQ capabilities. Ring Imaging Cerenkov RHIC Spin Overview

  13. STAR spin physics program: ∆G, ∆q/∆q, Sivers, δq Large acceptance TPC and EMC -1<η<2 RHIC Spin Overview

  14. RHIC Detector Status and Upgrades o All instrumentation is in place for the planned measurements on spin dependent gluon distributions and transverse spin. o W-physics (flavor separation of quark and anti-quark polarizations) requires upgrades in PHENIX (muon trigger, funded by NSF and JSPS) and STAR (forward tracking, grant proposal to DOE in preparation). o In PHENIX a central silicon tracking upgrade and a forward tungsten silicon calorimeter upgrade will significantly enhance capabilities for jet and photon-jet physics. o A RHIC luminosity upgrade (RHIC II) for heavy ions with electron cooling will gain a factor 3-5 (beyond design) in luminosity from 2012. RHIC Spin Overview

  15. Gluon Spin Distribution ALL in inclusive Jets (STAR) ALL for inclusive π0 (PHENIX)

  16. ALL from Inclusive Jets in p+p Collisions at √s=200GeV jet cone=0.4 STAR Preliminary STAR Projections for 2006 *) Predictions: B.Jager et.al, Phys.Rev.D70(2004) 034010 J. Kiryluk, spin: Sa 9:00 • Results limited by statistical precision • Total systematic uncertainty ~0.01 (STAR) + beam pol. (RHIC) • GRSV-max gluon polarization scenario disfavored RHIC Spin Overview

  17. Run 5 ALL(p0): First constraints for ∆G(x) Comparision with ∆G from QCD analysis of DIS data: M. Glück, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775. M. Liu, spin: Sa 9:20 Y. Fukao, spin: Sa 9:40 max ∆G from DIS Excludes large gluon spin contributions! Needs to be quantified with NLO pQCD analysis! standard ∆G from DIS min ∆G possible ∆G =0 40% scale error (missing abso- lute polarization measurement). ¨ RHIC Spin Overview

  18. NLO QCD Analysis of DIS A1 + ALL(π0) M. Hirai, S. Kumano, N. Saito, hep-ph/0603212 (Asymmetry Analysis Collaboration) M. Hirai, spin: Sa 12:10 DIS A1 + ALL(π0) ACC03 x RHIC Spin Overview

  19. NLO QCD Analysis vs High pT Hadron Production in DIS High pT hadron production provides additional constraints to fit for 0.07 < x < 0.3, high pT data consistent with the three fit results for ΔG/G DIS A1 + ALL(π0) DIS A1 DIS A1 + ALL(π0) + neg ΔGinitial RHIC Spin Overview

  20. ∆G Measurements by 2012 see Spin report to DOE http://spin.riken.bnl.gov/rsc/ s=200 GeV incl. 0 prod’n s=500 GeV incl. jet prod’n • Final results on ∆G will come from combined NLO analysis of all channels at RHIC and in DIS • RHIC measurements will span broad range in x with good precision. multiple channels with independent theo. and exp. uncertainties. • Uncertainty through extrapolation to small x RHIC Spin Overview

  21. Transverse Spin AN for inclusive hadrons (BRAHMS, PHENIX, STAR) C. Cagliardi, spin: Fr14:20 K. Tanida, spin: Fr14:40 J.H. Lee, spin: Fr15:00

  22. QCD Cross Sections for Transverse Spin QCD: Asymmetries for transverse spin are small at high energies (Kane, Pumplin, Repko, PRL 41, 1689–1692 (1978) ) Experiment (E704, Fermi National Laboratory): π+ QCD Test ! π0 π- Suggestions: Sivers-, Collins-, Qui-Sterman, Koike mechanisms !? Can QCD be re-conciled with large transverse asymmetries? RHIC Spin Overview

  23. STAR: AN for backward angles from 2003 data PHENIX AN(π0) and AN(π0)at |η|<0.35 Phys.Rev.Lett.95:202001,2005 STAR AN(π0) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 and (hep-ex/0502040) K. Tanida, spin: Fr14:40 C. Cagliardi, spin: Fr14:20 update! • Sizable asymmetries for xF > 0.4 • Back angle data consistent with AN ~ 0 • Updated results in parallel session! RHIC Spin Overview

  24. BRAHMS: AN for charged pions J.H. Lee, spin: Fr15:00 AN for pions: AN= +0.05 +- 0.005 +- [0.015] pT vs XF AN= -0.08 +- 0.005 +- [0.02] in 0.17 < xF < 0.32 xF x 100 • o Expect new results from run 2005 for • pions but also kaons and protons. • What can be learned by analyzing precision RHIC data on AN for different kinematics and different final state hadrons (Collins effect for kaons, protons)? xF x 100 RHIC Spin Overview

  25. Large AN: mainly two mechanisms M. Anselmino, M. Boglione, U. D’Alesio, E. Leader, S. Melis and F. Murgia hep-ph/0601205 (I) Sivers quark and gluon distributions Correlation between proton-spin and transverse quark momentum quark-Sivers (II) Transversity quark-distributions and Collins fragmentation Correlation between proton- und quark-spin and spin dependent fragmentation Transverstiy x Collins gluon-Sivers RHIC Spin Overview

  26. Back-to-back di-Jets: Access to Gluon Sivers Function Measurements near mid-rapidity with STAR – search for spin-dependent deviation from back-to-back alignment > 7 GeV trigger jet > 4 GeV away side jet Current measurements should be sensitive at the level of predictions D. Boer and W. Vogelsang, Phys.Rev. D 69 (2004) 094025 PHENIX: measurement of back-to-back di-hadrons. RHIC Spin Overview

  27. Measurement of Transverse Parton Distributions at RHIC luminosity sufficient? AN yes, very good AN(back-to-back) good (Sivers signature!) AT (Collins FF in jets) fair AT (Interference FF) fair ATT (Jets) systematics limited AT (Drell Yan) ATT( Drell Yan) Direct photons (AN,AT(CFF, IFF)) RHIC by 2009 at 200 GeV ∫Ldt ~275pb-1delivered ∫Ldt ~100pb-1 accepted (eg. PHENIX: vertex cut, trigger efficiencies, duty factor)  ∫Ldt ~25 pb-1 transverse RHIC II RHIC Spin Overview

  28. Collins Function Measurement in e+e- at Belle e+e- CMS frame: R. Seidl, spin: Th 17:30 j2-p e- Q j1 j2 j1 e+ 2-hadron inclusive transverse momentum dependent cross section: RHIC Spin Overview

  29. LO-QCD Analysis of HERMES and Belle Results (Efremov, Goeke, Schweitzer, hep-ph/0603054) HERMES PRELIMINARY BELLE PRELIMINARY Combined fit to Hermes asymmetries (Transversity x Collins-FF) and Belle asymmetries (Collins-FF2)  Excellent agreement! RHIC Spin Overview

  30. Plans for the measurement of spin dependent quark and anti-quark in W-production at RHIC

  31. Projected Sensitivities in PHENIX • Machine and detector requirements: • ∫Ldt=800pb-1, P=0.7 at √s=500 GeV • required upgrades: high rate muon trigger (PHENIX) high momentum tracking (STAR) 2009 to 2012 running at √s=500 GeV is projected to yield ∫Ldt ~950pb-1 RHIC Spin Overview

  32. Summary RHIC and it’s experiments are the world’s first facility capable of colliding high energy polarized protons (and heavy ions). Collider and Experiments are complete and a first high Statistics polarized took place in 2005. Run 2006 consists of 16 weeks for proton-running. Polarized Protons at RHIC provide a powerful experimental tool to study the structure of the nucleon. We are at the beginning of a broad new program on nucleon substructure. RHIC Spin Overview

  33. Physics vs Luminosity and Polarization at RHIC see Spin report to DOE http://spin.riken.bnl.gov/rsc/ L= 1x1031cm-2s-1 6x1031cm-2s-1 1.6x1032cm-2s-1 P= 0.5 0.6 0.7 …………………………………… √s= ……………………….. 200 GeV …………………......... 500 GeV| 2005 2006 2007 2008 2009 …. 2012 (RHIC II) 10 pb-1 …………………………………… 275pb-1 …….. 950pb-1 @ 200GeV @ 500GeV Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics direct photons bottom physics W-physics ALL(hadrons, Jets) ALL(charm) AL(W) ALL(γ) RHIC Spin Overview

  34. Carbon CNI Polarimeter in the AGS: Polarization during Acceleration each point = 50 MeV step raw asymmetry = AN· PB intrinsic: Gg = imperfection: Gg = n 12+n 36-n Gg = 1.91 Ebeam 48-n 36+n red line: simulation of polarization losses assuming constant AN RHIC Spin Overview

  35. Run 04+05: The Polarized Jet Target for RHIC Courtesy Sandro Bravar, and Yousef Makdisi • Polarized Hydrogen Gas Jet Target • thickness of > 1012p/cm2 • polarization > 92.4% (+/-2)%! • no depolarization from beam wake fields • Silicon recoil spectrometer to measure • The left-right asymmetry AN in pp elastic scattering in the CNI region to AN < 10-3 accuracy. • Transfer this to the beam polarization • Calibrate the p-Carbon polarimeters • 2004 analysis Pb = 0.39+/-0.03 RHIC Spin Overview

  36. Jet Profile and TOF vs Energy JET Profile: measured selecting pp elastic events recoil protons elastic pp pp scattering FWHM ~ 6 mm as designed D ToF < ± 8 ns background 118 cts. subtracted Number of elastic pp events T Kin [MeV] CNI peak AN 1 < EREC < 2 MeV  source calibration Hor. pos. of Jet 10000 cts. = 2.5 mm prompt events and beam-gas • recoil protons unambiguously identified ! ToF vs EREC correlation Tkin= ½ MR(dist/ToF)2 RHIC Spin Overview

  37. Bunch shuffle 1<pT<2 GeV/c 2<pT<3 GeV/c 3<pT<4 GeV/c 4<pT<5 GeV/c • Randomly reassign helicity for each fill and recalculate asymmetry. • Do 1000 times and look at c2 distribution. • Agree with expected distribution • Bunch to bunch systematics smaller than current statistics. 5<pT<6 GeV/c 6<pT<7 GeV/c 7<pT<8 GeV/c 8<pT<9 GeV/c RHIC Spin Overview

  38. Run5 p0 Cross Section • Consistent with previous PHENIX results from runs 3+4 • Extends previous results to pT of 20 GeV/c. • Theory is consistent with data over nine orders of magnitude. 2005 preliminary p0 cross section vs perturbative QCD (W. Vogelsang) (Data – Theory)/Theory RHIC Spin Overview

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