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Hadron Physics at RHIC

Hadron Physics at RHIC. M. Grosse Perdekamp UIUC and RBRC. STAR. RHIC Physics Low x  Saturation? Access to Nucleon Structure? pQCD vs Experiment Proton Spin Structure RHIC and Experiments Gluon Spin Transverse Spin. pp2pp.

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Hadron Physics at RHIC

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  1. Hadron Physics at RHIC M. Grosse Perdekamp UIUC and RBRC STAR • RHIC Physics • Low x  Saturation? • Access to Nucleon Structure? • pQCD vs Experiment • Proton Spin Structure • RHIC and Experiments • Gluon Spin • Transverse Spin pp2pp Observables in Antiproton-Proton Interactions and their Relevance to QCD

  2. 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) very active field: eg. 76 Physical Review Letters in the first 5 years with more than 6800 citations in SPIRES Hadron Physics at RHIC

  3. 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, Lambda production (1) AN (2) ATT in Collins- and Interference-Fragmentation (3) ATT and AT In Drell Yan Hadron Physics at RHIC

  4. Heavy Ion Physics • Structure of Neutron Stars • physics goal to find quark matter and survey it’s properties experimental method heavy ion collisions at high energies Hadron Physics at RHIC

  5. Heavy Ion Physics A brief history of Heavy Ion Experiment Bevalac AGS GSI SPS RHIC LHC Find quark matter and survey it’s properties Hadron Physics at RHIC

  6. RHIC 2001 – 2005 : the sQGP ! Key Observations • Jets are suppressed in central Au + Au collisions • Suppression is flat up to pt ~ 10 GeV/c • Absence of suppression in d+Au • Strong elliptic flow • Scaling of v2 with eccentricity shows that a high degree of collectivity builds up at a very early stage of collision – evidence for early thermalization • Data described by ideal hydrodynamic models fluid description of matter applies. • Energy density allows for a non-hadronic state of matter • Energy density estimates from measurements of dN/dy are well in excess of the ~1 GeV/fm3 lattice QCD prediction for the energy density needed to form a deconfined phase. Strongly interacting Quark Gluon Plasma ! Hadron Physics at RHIC

  7. Is the Initial State in Heavy IonCollisions Determined by Saturation Effects in the Gluon Field ?

  8. BRAHMS d+Au Results as Function of Rapidity and Centrality BRAHMS, PRL 93, 242303 and R. Debbe YdAu RdAu= NcollYpp Hadron production is suppressed at large rapidity consistent with saturation effects at low x in the Au gluon densities  CGC Hadron Physics at RHIC

  9. Similar Effects Seen by PHENIX and PHOBOS PRL 94, 082302 Suppression in the d direction and enhancement in the Au frag. region Hadron Physics at RHIC

  10. Saturation Picture (CGC) Consistent with Data A. Dumitriu et al. Nucl. Phys. A770 57-70,2006 Not bad! However, Large K factors, η-dependent. We hope for NLO calculations soon … Hadron Physics at RHIC

  11. Access to Nucleon Structure inHadron Collisions?

  12. Access to Nucleon Structure at RHIC Measure: (spin dependent) cross sections QCD analysis: (spin dependent) distribution functions Hadron Physics at RHIC

  13. Example: DG(x) from global NLO pQCD analysis using projected future direct photon data from RHIC QCD analysis of inclusive DIS data QCD analysis DIS data + future direct photons M. Hirai, H.Kobayashi, M. Miyama et al. (Asymmetry Analysis Collaboration) Hadron Physics at RHIC

  14. Example: ΔG(x) from global NLO pQCD analysis using projected future direct photon data from RHIC 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) Hadron Physics at RHIC

  15. Is pQCD applicable in p-p Collisions ? • Tevatron data as input to CTEQ • QCD analysis of hard scattering • data, specifically: G(x,Q2) • Comparison: • NLO pQCD vs RHIC data •  inclusive hadrons •  inclusive jets •  direct photons Hadron Physics at RHIC

  16. CTEQ 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 Hadron Physics at RHIC

  17. 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 Hadron Physics at RHIC

  18. Data vs NLO pQCD at RHIC: Inclusive π0 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 NLO QCD from W. Vogelsang Hadron Physics at RHIC

  19. Direct Photons and Inclusive Jets vs NLO pQCD Direct Photon Cross section Inclusive Jet Cross section NLO QCD from W. Vogelsang PHENIX Preliminary Theory calculation show good agreement with the experimental cross section. STAR Preliminary NLO QCD from W. Vogelsang Hadron Physics at RHIC

  20. Direct Photons in Heavy Ion Collisions Use hard probes (hadrons vs direct photons) to study medium formed in heavy ion collisions at RHIC quark  jet g q direct photon Hadron Physics at RHIC

  21. Collision Geometry: Impact Parameter vs Collisions and Participants Spectators Participants Npart ~ (No. participants) Nbinary ~ (No. binary collisions) 15 fmb 0 fm 0 Npart 394 0 Nbinary 1200 Hadron Physics at RHIC

  22. pQCD vs Direct Photons in Au+Au PRL 94, 232301 pQCD x number of binary nucleon-nucleon collisions, Nbinary , in heavy in collisions (Werner Vogelsang) pQCD calculations permit “calibration” of hard probes in heavy ion collisions at RHIC in a model indepen- dent way Hadron Physics at RHIC

  23. pQCD vs Inclusive Hadrons: “Jet Suppresion” • Suppression is strong (factor 5) up to 20 GeV/c • Medium is extremely opaque • The data provide a lower bound on the initial gluon density pp comparison data (and pQCD!) Hadron Physics at RHIC

  24. RHIC

  25. RHIC: ion-ion and polarized p-p Collider Hadron Physics at RHIC

  26. RHIC  five complementary experiments pp2pp Hadron Physics at RHIC

  27. Run 2006 ∫Ldt ~ 23.5 pb-1 Polarization average 60% A novel experimental method: Probing Proton Spin Structure Through High Energy Polarized p-p Collisions RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes BRAHMS & PP2PP PHOBOS 2005 Complete! high current polarized source helical dipoles magnets high energy proton polarimetry Siberian Snakes Spin Flipper PHENIX STAR Spin Rotators Partial Snake Strong Snake Helical Partial Snake Polarized Source LINAC AGS BOOSTER 200 MeV Polarimeter Rf Dipole AGS Polarimeter Hadron Physics at RHIC

  28. 2006: Figure of Merit Goals and Actual goals 0.88 1.11 ~7 times Run-5 P2L: Transverse P4L: Longitudinal Hadron Physics at RHIC

  29. BRAHMS: AN for charged π,K, p, low x 100% transverse spin! Two spectrometer arms with good particle ID at high momenta Hadron Physics at RHIC

  30. PHENIX: ∆G, ∆q/∆q, Sivers, δq, low x 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 Hadron Physics at RHIC

  31. STAR: ∆G, ∆q/∆q, Sivers, δq, low x Large acceptance TPC and EMC -1<η<2 Hadron Physics at RHIC

  32. 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. Hadron Physics at RHIC

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

  34. 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 • Results limited by statistical precision • Total systematic uncertainty ~0.01 (STAR) + beam pol. (RHIC) • GRSV-max gluon polarization scenario disfavored Hadron Physics at RHIC

  35. Run 5 ALL(p0): First constraints for ∆G(x) Comparison with ∆G from QCD analysis of DIS data: M. Glück, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775. 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). ¨ Hadron Physics at RHIC

  36. NLO QCD Analysis of DIS A1 + ALL(π0) M. Hirai, S. Kumano, N. Saito, hep-ph/0603212 (Asymmetry Analysis Collaboration) DIS A1 + ALL(π0) ACC03 x Hadron Physics at RHIC

  37. ∆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 Hadron Physics at RHIC

  38. Transverse Spin AN for inclusive hadrons (BRAHMS, PHENIX, STAR)

  39. QCD Cross Sections for Transverse Spin QCD: Asymmetries for transverse spin are small at high energies (Kane, Pumplin, Repko, PRL 41, 1689–1692 (1978) ) QCD Test ! Hadron Physics at RHIC

  40. 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+ π0 π- Suggestions: Sivers-, Collins-, Qui-Sterman, Koike mechanisms !? Can QCD be re-conciled with large transverse asymmetries? Hadron Physics at RHIC

  41. AN Results from PHENIX and STAR 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) • Sizable asymmetries for xF > 0.4 • Back angle data consistent with AN ~ 0 Hadron Physics at RHIC

  42. BRAHMS AN Pions p+ p Protons p- p K+ Kaons • DIS 2006, prel. stat. errors only • First AN for kaons and protons • AN(K-) and AN(p) don’t agree with naive expectation from valence quark fragmentation K- Hadron Physics at RHIC

  43. AN: Maximum Asymmetries Possible 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 (II) Transversity quark-distributions and Collins fragmentation Correlation between proton- und quark-spin and spin dependent fragmentation quark-Sivers Transversity x Collins gluon-Sivers RHIC 2006: precision measurements of AN with ~ 20 x ∫Ldt and 2-3 x Pbeam on tape:  QCD analysis to separate effects !? Hadron Physics at RHIC

  44. Measurement of Transversity- and Sivers-Distributions in Polarized p-p Collisions at RHIC RHIC Luminosity? AN excellent! AN(jet/hadron-correlations) good (Sivers signature!) AT (Collins FF) just enough AT (Interference FF) just enough AT (Drell Yan) no ATT( Drell Yan) no requires Collins and Interference FFs  e+e- at Belle RHIC II Luminosities Hadron Physics at RHIC

  45. RHIC II Luminosity UpgradeTransversity & Sivers & Boer-Mulders in Drell Yan Transversity : correlation between transverse proton spin and quark spin Sivers : correlation between transverse proton spin and quark transverse momentum Boer/Mulders: correlation between transverse quark spin and quark transverse momentum Hadron Physics at RHIC

  46. Sivers-Asymmetries, AT in Drell Yan (J. Collins et al.) Q=4GeV Q=4GeV Q=20GeV Q=20GeV AT AT STAR for 125pb-1 Dedicated DY Experiment 1250 pb-1 o 10 o’clock  100% transverse polarization o mini-quads o acceptance: -3 < η < 3 Hadron Physics at RHIC

  47. Transversity in Drell Yan with a Dedicated Drell Yan Experiment for Transverse Spin ATT for Drell Yan with dedicated DY detector projections for 1250pb-1 of running, 5-10% higher polarization, with RHIC II luminosities and large acceptance Drell Yan 1.25fb-1, large acceptance detector for Drell Yan This measurement appears to be also possible at 500 GeV Hadron Physics at RHIC

  48. 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 first high statistics polarized proton runs took place in 2005 and 2006. Hadron Collisions 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 spin dependent nucleon substructure and phenomena in nucleon structure at low x. Hadron Physics at RHIC

  49. 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 Hadron Physics at RHIC

  50. 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. Hadron Physics at RHIC

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