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RHIC Spin Physics

RHIC Spin Physics. G. Bunce Workshop on HEP in the LHC Era Valparaiso December 2006. RHIC Spin Program. Direct measurement of polarized gluon distribution using multiple probes Direct measurement of anti-quark polarization using parity violating production of W+/-

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RHIC Spin Physics

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  1. RHIC Spin Physics G. Bunce Workshop on HEP in the LHC Era Valparaiso December 2006

  2. RHIC Spin Program • Direct measurement of polarized gluon distributionusing • multiple probes • Direct measurement of anti-quark polarization using • parity violating production of W+/- • Transverse spin: Transversity & transverse spin effects: • possible connections to orbital angular momentum? • Also: • Transverse and double spin asymmetries for pp elastic • scattering in CNI region (polarized jet target), pC, pp at • collider energy • Very forward neutron asymmetry (transverse spin)

  3.  calculate measure  learn about ! parton scatt. perturbative QCD universal • this is formalized through “factorization theorems”

  4. Probing the spin structure of the nucleon in polarized pp collisions

  5. RHIC Polarized Collider RHIC pC Polarimeters Absolute Polarimeter (H jet) BRAHMS & PP2PP PHOBOS Siberian Snakes Siberian Snakes PHENIX STAR Spin Rotators (longitudinal polarization) Spin Rotators (longitudinal polarization) Pol. H- Source LINAC BOOSTER Helical Partial Siberian Snake AGS 200 MeV Polarimeter AGS pC Polarimeter Strong AGS Snake 2006: 1 MHz collision rate; P=0.6

  6. STAR spin physics program: ∆G, ∆q/∆qbar, transverse spin FMS Large acceptance TPC and EMC -1<η<2

  7. PHENIX spin physics program: ∆G, ∆q/∆qbar, transverse spin 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

  8. Braod RAnge Hadron Magnetic Spectrometers • Designed to study nuclear reactions in broad kinematic range (y-pT) • 2 movable spectrometers with small solid angle measuring charged identified hardrons precisely • Min-Bias Trigger Detector for pp: ”CC” counter • 53 people from 12 institutions from 5 countries

  9. Cornerstones to the RHIC Spin program pp   X 0 QCD prediction Mid-rapidity: PHENIX Physical Review Letters 91, 241803 (2003)

  10. Cornerstones (continued) 0 pp   X Forward rapidity: STAR

  11. Direct Photon 2005 data From Run5 data X10 luminosity of Run3 • Pi0 tagging method and isolation cut method • PRL on 2003 data soon • Described by pQCD over 4 orders of magnitude

  12. Ratio of the direct photon • Theory curves • Two fragmentation functions • Three scales • Direct photons are isolated and isolation is described by theory (pT>7GeV/c) • For low pT region underlying event not included, may contribute to reduced isolation • Pi0 photons (from jet) are not isolated

  13. Siberian Snakes 2003-4: Warm AGS Snake 1996-2001: Siberian Snakes Snake: precess spin, leaving beam direction unchanged at exit of snake

  14. Exquisite Control of Systematics

  15. Polarimetry scattered proton polarized beam 0.01 < |t| < 0.02 (GeV/c)2 Carbon target recoil Carbon

  16. Raw asymmetries from carbon polarimeter by bunch (2005)

  17. RHIC Polarimetry Jet Polarization • PHOTO of Jet Pol

  18. Polarization Measurements 2006 Run

  19. Measurement of the Analyzing Power AN in pp elastic scattering in the CNI region with a Polarized Atomic Hydrogen Gas Jet Target • RUN4 -JET commissioning • (2004 April 26th -May 14th) • H-Jet target pol. ; 0.924  0.018! • 0.001 < -t < 0.032 (GeV/c)2 • Data taking: • 100GeV/c proton beam (s=13.7 GeV) • 90hours, 4.3M elastic events • PLB 638 (2006), 450-454 • 24GeV/c proton beam (s=6.9 GeV) • 16 hours, 0.8M elastic events Today’s topics; New AN and ANN results at s = 6.9 GeV Hiromi Okada from RIKEN I. Alekseev, A. Bravar, G. Bunce, S. Dhawan, O. Eyser, R. Gill, W. Haeberli, O. Jinnouchi, A. Khodinov, K. Kurita, Z. Li, Y. Makdisi, I. Nakagawa, A. Nass, S. Rescia, N. Saito, H. Spinka, E. Stephenson, D. Svirida, T. Wise, A. Zelenski

  20. Transverse spin dependent asymmetries of pp elastic scattering as a function of -t Forward scattered proton • Single spin asymmetry • Double spin asymmetry proton beam proton target Recoil proton

  21. Measurements of AN & ANN in the CNI region @ s=13.7 GeV s=13.7 GeV PLB 638 (2006), 450-454 Set r5 as free parameter:  2/ndf = 11.1/12  Im r5 = 0.015  0.029  Re r5 = 0.0008  0.0091  |r5| is consistent with zero! |r5| =0 • Compare measured AN and expected curve with |r5| =0  2/ndf = 13.4/14, |r5| is consistent with zero! 2had and 5hadare consistent with zero at s = 13.7 GeV. • Measured ANN at s = 13.7 GeV are consistent with zero!  <ANN> = 0.0024  0.0015

  22. AN and r5 results at s= 6.9 GeV • 0.8 M ppelastic events. • Errors on the data points are statistics only. • Components of systematic errors • Acceptance asymmetry • Background correction • Elastic event selection • Set r5 as free parameter •  Im r5 = 0.152  0.014 •  Re r5 = 0.045  0.038 • 2/ndf = 2.87/7 preliminary |r5|=0 • r5 is not zero at s=6.9 GeV ! 2/ndf = 35.5/9 • r5 has s dependence ?  Not improbable; theoretical prediction using ANpC @24GeV/c, 100GeV/c and AN @100GeV/c.

  23. AN collection in the CNI region Pbeam=24 GeV/c Pbeam=100 GeV/c ANpp |r5|=0 |r5|=0 preliminary Theoretical interpretation is undergoing! Next inputs: RUN6 s = 7.6 GeV data ~1 week (31 GeV/c beam) Pbeam=21.7 GeV/c J. Tojo et al. Pbeam=100 GeV/c O. Jinnouchi et al. ANpC |r5|=0 |r5|=0 preliminary

  24. ANN results at s=6.9 and 13.7 GeV • Errors on the data points are statistics only • Components of systematic errors • Relative luminosity of RHIC-beam and H-jet-target • Polarization of RHIC-beam • Background correction • Event selection preliminary • Mean value for all –t range: • <ANN> = -0.0056  0.0036 at s = 6.9 GeV •  Consistent with <ANN> = -0.0024  0.0015 at s = 13.7 GeV

  25. Pp2pp: root(s)=200 GeV A_N: PL B632, 167 (2006) Submitted: A_NN = 0.030 +/- 0.017 +/- 0.005 A_SS = 0.004 +/- 0.008 +/- 0.003

  26. Measurement of the cross section and the single transverse spin asymmetry of forward neutrons from p-p collisions at RHIC-PHENIX Manabu Togawa for the PHENIX collaboration. Kyoto University / RBRC

  27. pT distribution is assuming ISR result Cross section Integrated pT area : 0<pT<0.11xF GeV/c in each point. Cross section result is consistent with ISR data and xF scaling holds at such higher energy.

  28. charged particles neutron neutron ypos Single transverse spin asymmetry • Smearing effect is evaluated by simulation. • For asymmetry calculation, square root formula is used. xpos Expected mean pT (Estimated by simulation assuming ISR pT dist.) 0.4<|xF|<0.6 0.088 GeV/c 0.6<|xF|<0.8 0.118 GeV/c 0.8<|xF|<1.0 0.144 GeV/c preliminary * Cut is not same

  29. Measuring the proton spin structure… Quarks contribute only 20%! pion quark quark gluon

  30. Recent Results from the STAR Longitudinal Spin Program Frank Simon, MIT, for the STAR Collaboration RHIC Spin Physics Workshop, RIKEN, Japan September 29-30, 2006 Outline Introduction The STAR Experiment Lambda Polarization Neutral Pions Charged Pions Inclusive Jets 2006 Projections

  31. Introduction: Inclusive Measurements • Longitudinal double spin asymmetry ALL for inclusive processes depends on the gluon polarization • Asymmetry also depends on particle type

  32. Reconstructing Jets detector • Midpoint Cone Algorithm (Tevatron II) • TPC pt for charged hadrons, EMC energy for e.m. showers • Cone radius of 0.4 in , seed energy 0.5 GeV • restricted to 0 <  < 1 for e.m energy • Jet axis for accepted jets restricted to 0.2 <  < 0.8 particle • E.M. Triggers are used to access jets at high pt • JetPatch (JP) trigger new in 2005! parton • Trigger efficiency: • Minbias • JP2 • HT2

  33. Inclusive Jet Cross Section First inclusive jet cross section result at RHIC (2004 data) • Sampled luminosity: ~0.18 pb-1 • Good agreement with NLO over 7 orders of magnitude (within systematic error) • Leading systematic uncertainty: 10% E-scale uncertainty  50% uncertainty on yield

  34. Inclusive Jet ALL: 2005 Result 2 / NDF to curves:(stat+syst error in quadrature) GRSV-STD: 1.1 G = G: 12 G = 0: 0.7 G = -G: 1.4 Rules out G=G Error bars are statistical Systematic band does not include 25% scale error from polarization

  35. Recent Results from PHENIX Longitudinal Spin Program Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration • Outline: • Quick Physics overview • RHIC and PHENIX, and ALL requirements • Run5 and Run6 new Results

  36. Run6 p0 ALL (200 GeV) • Run6 Data set from 2.0-2.7 times improvement on statistical uncertainties from Run5. • Variation due to LvL2 “turn on.” • Due to unreleased absolute polarizations, which act a scale factor in ALL and which contain correlated and uncorrelated part, we have not combined the two data sets. • For confidence levels, assume complete correlation. GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

  37. p0 ALL @ s=62 GeV • As there is no cross section at s=62 GeV, we do not calculate confidence levels. • Grey band is systematic uncertainty from relative luminosity, which is independent of pT. GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

  38. Comparison with 200 GeV • Converting to xT, we can get a better impression of the significance of the s=62 GeV data set, when compared with the Run5 preliminary data set. • Awaits the unpolarized cross section for estimating 62 GeV significance.

  39. RHIC Spin: gluon polarization sensitivity 2009 Project. 2005 Prelim. PHENIX pi0 40% Scale uncertainty not included 2003+4 Final STAR jet 2006 Project. (data on tape)

  40. u unpol. Dq-Dq at RHIC via W production Expected start: 2009

  41. Transverse Spin The RHIC (STAR and BRAHMS) results at forward rapidity demonstrate that large spin effects exist in the perturbative QCD regime. There are new results from Belle showing large fragmentation asymmetry for polarized quarks. New HERMES results show large asymmetries for orbital angular momentum effects in polarized proton.

  42. Physics with transverse spin at RHIC STAR data •Transverse Physics: Measurement of transversity and study of other transverse spin effects with possible connections to orbital angular momentum

  43. Measurements of Transverse Spin Effects with the Forward Pion Detector of STAR Larisa Nogach Institute of High Energy Physics, Protvino for the STAR collaboration • Outline • Motivation and previous measurements • Detector layout • Status of the analysis of Run 6 data and results • Plans for Run 7 and beyond • Summary

  44. STAR detector layout Run 6 – FPD++ • TPC: -1.0 <  < 1.0 • FTPC: 2.8 <  < 3.8 • BBC : 2.2 <  < 5.0 • EEMC: 1 <  < 2 • BEMC: -1 <  < 1 • FPD++/FPD:  ~ 3.3/-3.7 FPD++: engineering test of the Forward Meson Spectrometer

  45. Cell-by-cell calibration • gains are determined from π0 peak position in 2γ invariant mass distributions sorted by high towers • accuracy of the calibration is at the level of ~2%

  46. π0AN at √s=200 GeV – xF-dependence • AN at positive xF grows with • increasing xF • AN at negative xF is consistent • with zero • Run 6 data at <η>=3.7 are • consistent with the existing • measurements • Small errors of the data points • allow quantitative comparison • with theory predictions • Theory expects the reverse • dependence on η

  47. AN(pT) at xF > 0.4 Run3+Run5 data (hep-ex/0512013): • Online calibration of CNI • polarimeter • Hint of AN decrease with • increasing pT at pT~1-2 GeV/c • Run6 data: • more precise measurements • consistent with the previous runs in the overlapping pT region • complicated dependence on pT residual xF-dependence? => AN mapping in (xF,pT) plane is required

  48. BRAHMS—Kyoto Spin2006J.H. Lee • 2 energies (root(s)=200 GeV, 62 GeV • Show for 2.3 deg. forward production • Identified particles: pi+/-, K+/-, p, pbar

  49. AN(p) at 2.3 deg. at 200 GeV

  50. AN(p) at 62 GeV

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