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RHIC Spin Physics

RHIC Spin Physics. Workshop on Hadron Structure and Hadron Spectroscopy August 1-3, 2005 Charles University, Prague. M. Grosse Perdekamp (University of Illinois and RBRC). Overview. Scientific motivation Proton spin structure ∆G, ∆q/∆q, δ q from QCD analysis

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RHIC Spin Physics

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  1. RHIC Spin Physics Workshop on Hadron Structure and Hadron Spectroscopy August 1-3, 2005 Charles University, Prague M. Grosse Perdekamp (University of Illinois and RBRC)

  2. Overview • Scientific motivation • Proton spin structure • ∆G, ∆q/∆q, δq from QCD analysis • of polarized proton-proton collisions • Novel experimental tool • Polarized proton-proton collisions at high energies • The experiments • New from run 2005 • Initial results and outlook • Helicity distributions • Transverse spin physics • W-physics and upgrades RHIC Spin Overview

  3. Structure of the Basic Building Blocks of Matter vs Fundamental Forces in Nature measurements with new tools + better precision fundamental bound state of matter interaction between the constituents of the bound state theory predictions increasingly quantitative RHIC Spin Overview

  4. Structure of the Basic Building Blocks of Matter vs Fundamental Forces in Nature Example: Lamb Shift (1947)  QED pioneers QFT! Lamb Doppler free saturation spectroscopy hydrogen atom Quantum Electro Dynamics Lamb shift Tomonaga, Feynman, Schwinger RHIC Spin Overview

  5. Structure of the Basic Building Blocks of Matter vs Fundamental Forces in Nature Nucleon structure: DIS/QCD Friedman, Kendall, Taylor DIS Nucleon Quantum Chromo Dynamics quark structure Gell Mann Nakano, Nishijima RHIC Spin Overview

  6. Structure of the Basic Building Blocks of Matter vs Fundamental Forces in Nature DIS with polarized beams and targets Nucleon Quantum Chromo Dynamics quark helicity dis. Bjorken sum rule RHIC Spin Overview

  7. Proton Spin Structure in DIS Future progress on ∆G(x), the flavor separation of ∆q(x) and δq(x) in DIS appears best possible at future polarized high luminosity e-p collider 1975 – 2005 SLAC: E80, E130, E142, E143, E154, E155 CERN: EMC, SMC, COMPASS DESY: HERMES JLab : Halls A,B,C Parton Distribution functions (PDF): Helicity average distribution quarks q(x) : well known gluons G(x) : moderately well known Helicity difference distribution quarks ∆q(x) : moderately well known gluons ∆G(x) : unknown Helicity flip (transversity) distribution quarks δq(x) : unknown Field started with polarized source and targets about 1975 Yale/SLAC collaboration RHIC Spin Overview

  8. A novel experimental method: Probing Proton Spin Structure in High Energy Polarized Proton Collisions at RHIC RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes BRAHMS & PP2PP PHOBOS Siberian Snakes *Complete* Spin Flipper PHENIX STAR Run 04 Spin Rotators Partial Snake Helical Partial Snake Strong Snake Pb~45% , 55 bunches Polarized Source Run 05 LINAC AGS BOOSTER 200 MeV Polarimeter <Pb> = 45% Rf Dipole strong AGS snake installed AGS Internal Polarimeter AGS pC Polarimeter RHIC Spin Overview

  9. Proton Spin Structure in Polarized p-p Collisions in PHENIX Gluon polarization Flavor separation of quark polarizations Transverse spin struc- ture of the Nucleon available channels Inclusive jets, hadrons, photons and heavy flavor production Single lepton asymmetries AL(e,μ) in W-production (1) ATT with Collins- and Interfe- rence-FFs (2) AN + back-to-back correlations (3) ATT and AT In Drell Yan goals determine first moment of the spin dependent gluon Distribution. flavor separation of quark and anti-quark spin distributions measurements of Collins and Sivers distributions RHIC Spin Overview

  10. DG from a global NLO pQCD Analysis with projected future Direct Photon Data at 200 GeV from RHIC Does NLO pQCD provide a reliable framework for the interpretation of polarized proton data in terms of polarized parton distribution functions? M. Hirai, H.Kobayashi, M. Miyama et al. AAC Preliminary AAC Preliminary RHIC Spin Overview

  11. Is pQCD applicable at RHIC? • Can one extract G(x,Q2) from pp? • NLO pQCD vs RHIC data RHIC Spin Overview

  12. Global QCD Analysis for G(x,Q2)and q(x,Q2): J. Pumplin et.al JEHP 0207:012 (2002) CTEQ6: use DGLAP Q2-evolution of quark and gluon distributions to extract q(x,Q2) and G(x,Q2) from global fit to data sets at different scales Q2. error on G(x,Q2) +/- 10% Quark and Gluon Distributions H1 + Zeus F2 CTEQ6M up-quarks CDF + D0 Jets gluon CTEQ5M1 10-410-3 10-2 10-1 0.5 x error for d(x,Q2) error for u(x,Q2) down anti-down +/- 5% +/- 5% 10-410-3 10-2 10-1 0.5 x RHIC Spin Overview

  13. G(x,Q2) and q(x,Q2) + pQCD beautifully agree Tevatron + HERA! J. Pumplin et.al JEHP 0207:012 (2002) ZEUS F2 D0 Jet Cross Section RHIC Spin Overview

  14. and at RHIC ? q(x,Q2), G(x,Q2) and D(z,Q2) + pQCD are nicely consistent with experiment! 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 gluon fragmentation !? o Good agreement between NLO pQCD calculations and experiment  can use a NLO pQCD analysis to extract spin dependent quark and gluon distributions from RHIC data! RHIC Spin Overview

  15. Direct Photons: NLO pQCD vs RHIC data • NLO-pQCD calculation • Private communication with W.Vogelsang • CTEQ6M PDF. • direct photon + fragmentation photon • Set Renormalization scale and factorization scale pT/2,pT,2pT Theory calculation show good agreement with the experimental cross section. RHIC Spin Overview

  16. Experimental Method a) Experiments b) Polarized proton run 2005

  17. RHIC  four complementary experiments Two experimental tools neededfor experiments at polarized colliderso Local polarimeter to verify local spin orientationo Relative luminosity monitoringbunch sorted luminosity scalers! RHIC Spin Overview

  18. Top Interaction Vertex Left * Right Bottom BBC East 3.3<|h|< 5.0 BBC West Local Polarimetry in STAR and PHENIX STAR: PHENIX: Exploit AN in forward neutron production in ZDC (zero degree ha- dronic calorimeters) A(Φ) A(Φ) rotator on rotator off  PL/P > 0.99 blue & yellow RHIC Spin Overview

  19. Relative Luminosity • Error from relative luminosity R • Use BBC Counts to measure R • high statistics ( ~ 51%) • low background • Use ZDC as a cross-check • different systematics and kinematics • achieved high precision in Run03/04 ZDC/BBC R = (L++/L+-) < 2.5 x 10-4 • “bunch sorted” relative luminosity scaler • boards to record up to 24 different • monitors for each bunch crossing. RHIC Spin Overview

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

  21. STAR EMC upgra-des for RHIC Spin (Courtesy Steve Vigdor) e.g., STAR barrel (nearly completed) and endcap (completed 2005) em calorimeters permit triggering/reconstruction for jets, , 0, … 0 reconstr’n from 2 ’s in EEMC+SMD di-Jet Event pT (GeV/c) # Jets/Evt 2005 STAR online jet monitoring (TPC+BEMC) 

  22. PHENIX spin physics program: ∆G, ∆q/∆q, δq • 2 central arms: electrons, photons, hadrons • charmonium J/, ’ -> e+e- • vector mesonr, w,  -> e+e- • high pTpo, p+, p- • direct photons • open charm • hadron physics • 2 muon arms: • “onium” J/, ’,  -> m+m- • vector meson -> m+m- • open charm Excellent trigger and DAQ capabilities: multiple trigger signature important for spin physics can be taken in parallel with high bandwidth! See talks by D. Fields (overview), H. Torii (central arms) and Ming Liu (muon arms). RHIC Spin Overview

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

  24. RHIC Detector Status and Upgrades o All instrumentation is in place for the planned measurements on gluon polarization and transverse spin! o W-physics (flavor separation of quark and anti-quark polarizations) requires upgrades in PHENIX (muon trigger, funded by NSF) and STAR (forward tracking, grant proposal to DOE in preparation) which are planned to be complete by 2009 and 2010 respectively. o In PHENIX a central silicon tracking upgrade and a forward tungsten silicon calorimeter upgrade will significantly will 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 in luminosity from 2012. RHIC Spin Overview

  25. Polarized Proton Run 2005 projected maximum Projected minimum RHIC Spin Overview

  26. Did we meet our goals? (I) Sampled Luminosity PHENIX Goal 5.5 pb-1 Pbeam=45% delivered luminosity • 3.8 pb-1 (sampled) • 85x109 p-p collisions +0.16pb-1 transverse RHIC Spin Overview

  27. (II) Luminosity weighted Polarization luminosity weighted average polarizations goal 45% RHIC Spin Overview

  28. (III) Figure of Merit Pb2Py2∫Ldt PHENIX Goal 226 nb-1 recorded 206 nb-1 RHIC Spin Overview

  29. Transverse Polarization at pbeam = 205 GeV Polarization ~ 30% • Analyzing power of local • polarimeter roughly the • same at twice the energy! • Local Polarimeter can • be used at higher beam • energy needed for the • W-physics program Raw Yellow Beam =PbeamAN @ PHENIX RHIC Spin Overview

  30. Early Results and Outlook (I) Transverse Spin

  31. E704: AN • Fermilab E-704 reported large • asymmetries AN in pion productions The observed asymmetries could result from Transversity x Spin-dep.fragmentation (Collins-Heppelmann effect), or Sivers effect or Higher-twist effects • Sterman and Qiu Initial State Twist 3 • Koike Final State Twist or a combination of the above E704 • 0 – E704, PLB261 (1991) 201. • π+/- - E704, PLB264 (1991) 462. left right PT=0.5~2 GeV/c RHIC Spin Overview

  32. STAR: AN for backward angles from 2003 data PHENIX AN(π0) and AN(π0)at |η|<0.35 C. Aidala, DIS 2004, to be published STAR AN(π0) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 and (hep-ex/0502040) Run 5  reduce errors by a factor 3-5. RHIC Spin Overview

  33. BRAHMS: AN for charged pions 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 From the ongoing 2005 run the • statistical errors will be reduced • by a factor 6-7 • o New absolute RHIC polarimeter will • reduce the systematic error by a factor 4 • What can be learned from confronting model calculations with precision data on AN? xF x 100 RHIC Spin Overview

  34. AN for Protons from BRAHMS BRAHMS preliminary e • Proton AN is compatible with 0 • AN will be available for pions, kaons and protons from run 2005 • What do we learn from comparing AN for different fragmentation functions? RHIC Spin Overview

  35. Run 2006 High Precision Measurement of AN, Sivers from back-to-back Correlations STAR and PHENIX STAR, PHENIX and BRAHMS (I) (II) Boer and Vogelsang (hep-ph/0312320): azimuthal back to back correlation between hadrons in opposite hemisphere jets: STAR Phys. Rev. Lett. 92:171801, 2004 Clean channel for Sivers effect! Separation of intrinsic transverse quark spin (transversity) from trans- verse momentum effects (Sivers)? RHIC Spin Overview

  36. Sensitivity Check for Back-to-Back Sivers Asymmetry (based on 2003 pp sample) Full di-jet Sivers Reduced for polarization and, “di-hadron smearing” Run03 p+p gamma-charged, 0.35/pb • Given 0.35/pb of data, we should be able to get 1% statistical • significance in AN using gamma-charged measurements of jet dphi • Expected raw AN could be 3.5% • Could also be as low as 0.5%, or as large as 10% • x-dependence of Sivers? • Effects from P=0.5, jet angle not aligned with transverse polarization, • and fragmentation reduces raw AN to ~1.0% • Have not evaluated systematic errors yet (underlying event…) RHIC Spin Overview

  37. Transverse Spin Physics Channels at RHIC for “High” Luminosity STAR and PHENIX STAR and PHENIX W. Vogelsang and M. Stratmann, RBRC Wrkshp on Transversity (2000) J.C. Collins, Nucl. Phys. B396, 161(1993) J. Collins, S. Heppelmann, G. Ladinsky, Nucl.Phys. B420 (1994)565 R. Jaffe, X.Jin, J. Tang Phys. Rev. D57 (1999)5920 Statistical sensitivity for AT with 32pb-1 RHIC Spin Overview

  38. Transverse spin program in PHENIX (and STAR) is luminosity limited luminosity sufficient? AN yes, very good AN(back-to-back) good (Sivers signature!) AT (Collins FF) fair AT (Interference FF) limited ATT (Jets) not studied experimentally 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 • Dedicated Drell Yan experiment for transverse spin physics ? RHIC II RHIC Spin Overview

  39. Dedicated Experiment for Drell Yan ? Idea: Large acceptance calorimeter experiment at PHOBOS interaction point (10 o’clock) Physics: ATT(DY)  transversity AUT (DY )  Sivers ATT (Jets)  transversity, correlations unpolarized DY? Exp. Param.: Re-use existing EMC + HCAL elements, pad-chamber layer for charged particle tagging, BBC, ZDC (exists), utilize PHENIX FEE, DAQ and trigger for dead time free read out  -3<η<3, sample all verticies. Low cost? Advantages: - 100% transverse spin - take advantage of luminosity upgrades, large acceptance, wide vertex cuts and dead time free read out for maximum ∫Ldt RHIC Spin Overview

  40. Expected effective Luminosity in 10 weeks • 100% transverse running • 125pb-1 delivered in 10 weeks x 0.6 (vertex, trigger efficiency, DAQ dead time, up-time x 2.5 (e-cooling) x 4 (mini quads) x 8 (acceptance) = 6000 pb-1 RHIC Spin Overview

  41. Projections for pp at 200 GeV and 320pb-1 O. Martin, M. Stratmann, A. Schaefer, W. Voglesang, Phys.Rev.D60:117502,1999 ATT for Drell Yan with PHENIX Result includes acceptance for PHENIX muon arms or alternatively for muon arms + central arms RHIC Spin Overview

  42. Projections for pp at 200 GeV and 8000 pb-1 ATT for Drell Yan with PHENIX projections for 10 weeks of running, 5-10% higher polarization, with RHIC II luminosities and large acceptance Drell Yan 8fb-1, large acceptance detector for Drell Yan This measurement appears to be also possible at 500 GeV RHIC Spin Overview

  43. Early Results and Outlook (II) Longitudinal Spin

  44. First Exploratory Results on ∆G PHENIX Data appears to prefer the GRSV- standard curve, consistent with the existing constraints from DIS QCD analysis. B. Jaeger et al. Phys. Rev. D67, 054005 (2003) Statistical resolution comparable to existing information - QCD analysis of g1(x,Q2) - from DIS experiments. PHENIX ALL for Inclusive π0 productionat √s=200 GeV, 2003 + 2004 data with about ∫Ldt~0.3pb-1 and <Pb>~0.3 Preliminary Run 5 (April –June 2005): absolute polarimeter gives ∆Pb/Pb~7% ∫Ldt ~ 3pb-1, <Pb>~0.45  reduces statistical error by factor 7 RHIC Spin Overview

  45. Expectations from Run 2005 ALL in inclusive jet production (STAR) Jager, Stratmann, Vogelsang hep-ph/0404057 ALL(Jets) ∫Ldt=3pb-1 P=0.4 Input: ∆G(x)=G(x) GRSV: standard ∆G(x) ∆G(x)=0 ∆G(x)= -G(x) pT [GeV/c] ALL in inclusive π0 production (PHENIX) Vogelsang hep-ph/0405069 ALL(π0) ∫Ldt=3pb-1 P=0.4 Input: ∆G(x)=G(x) GRSV: standard ∆G(x) ∆G(x)= -G(x) ∆G(x)=0 pT [GeV/c] • GRSV standard ∆G(x) • Gluon distribution from NLO pQCD fit to DIS data on A1, Gluck Reya, Stratmann, Vogelsang Phys. Rev. D63:094005, 2001 run 05: ∫Ldt ~ 3.0 pb-1 P =0.45 RHIC Spin Overview

  46. ∆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 RHIC and 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

  47. 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

  48. Outlook (III) W physics (IV) Upgrades

  49. W Production in Polarized pp Collisions Single Spin Asymmetry in the naive Quark Parton Model Parity violation of the weak interaction in combination with control over the proton spin orientation gives access to the flavor spin structure in the proton! Experimental Requirements:  tracking at high pT event selection for muons difficult due to hadron decays and beam backgrounds. W Z RHIC Spin Overview

  50. Quark Polarizations through Inclusive Single Longitudinal Spin Lepton Aymmstries AL(lepton) • Access to quark polarizations through measurements of inclusive longitudinal single spin asymmetry? • Yes! Complete theoretical treatment from first principles by Nadolsky and Yuan at NLO pQCD (Nucl. Phys.B 666(2003) 31). • Machine and detector requirements: • ∫Ldt=800pb-1, P=0.7 at √s=500 GeV • Upgrades: o Muon trigger in PHENIX o Forward tracking in STAR pTm[GeV] RHIC Spin Overview

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