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

RHIC Spin Overview2 April 20 th RHIC  five complementary experimentsRHIC: ion-ion and polarized p-p Collider pp2pp

RHIC Spin Overview3 April 20 th Physics at the Relativistic Heavy Ion Collider o Quark Matter at high Temperatures and Densities ion-ion collisions (Cu-Cu, Au-Au: √s NN =22.5, 62, 130, 200 GeV) o Proton Spin Structure polarized proton-proton collisions (p-p: √s=200 to 500 GeV) o Low-x and high parton densities ion-deuteron collisions (d-Au: √s NN =200 GeV) C. Cagliardi low-x: Sat very active field: eg. 74 PRL letters in the first 5 years

RHIC Spin Overview4 April 20 th available channels jets, hadrons, photons, photon-jet, heavy flavor Single spin lepton asym- metries in W-production (1) A N (2) A TT in Collins- and Interference-Fragmentation (3) A TT and A T In Drell Yan 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 Proton Spin Structure in Polarized p-p Collisions at RHIC

RHIC Spin Overview5 April 20 th Access to Parton Distributions at RHIC Measure: (spin dependent) cross sections QCD analysis: (spin dependent) distribution functions

RHIC Spin Overview6 April 20 th Example:  G(x) from a global NLO pQCD analysis with projected future direct photon data from PHENIX M. Hirai, H.Kobayashi, M. Miyama et al. (Asymmetry Analysis Collaboration) 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

RHIC Spin Overview7 April 20 th Inclusive Hadron Cross Sections vs NLO QCD PHENIX π 0 cross section a |η|<0.35 Phys.Rev.Lett.91:241803,2003 STAR π 0 cross section a 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004

RHIC Spin Overview8 April 20 th Theory calculation show good agreement with the experimental cross section. Direct Photons and Inclusive Jets vs NLO pQCD M.Miller, hadronic final states: Sat Inclusive Jet Cross sectionDirect Photon Cross section STAR Preliminary 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! M. Stratmann, spin: Fr 16:30 Theory perspective:

RHIC Spin Overview April 20 th AGS LINAC BOOSTER Polarized Source Spin Rotators Partial Snake Siberian Snakes 200 MeV Polarimeter AGS Polarimeter Rf Dipole RHIC pC Polarimeters Absolute Polarimeter (H jet) P HENIX P HOBOS B RAHMS & PP2PP S TAR Siberian Snakes Helical Partial Snake Strong Snake Spin Flipper 2005 Complete! A novel experimental method A novel experimental method: Probing Proton Spin Structure Through High Energy Polarized p-p Collisions high current polarized source high energy proton polarimetry helical dipoles magnets Last Week at RHIC peak average  design L P 67% 61% 70% Luminosity in cm -2 s -1 A. Bravar, spin: Fr 16:10 Generous support from RIKEN, Japan and DOE

RHIC Spin Overview10 April 20 th Polarized p-p at RHIC: Detector Instrumentation (I)Upgrades to adapt “heavy ion detectors” for high rate p-p environment (eg. PHENIX trigger, STAR EMC, STAR tracking at high momentum) (II)Local polarimeters to verify polarization direction at the interaction point (important for longitudinal spin!) (III)Relative luminosity: arises in calculating asymmetries between yields from different bunch crossings, say i and j eg. F. Simon, spin: Sa10:20

RHIC Spin Overview11 April 20 th 100% transverse spin! Two spectrometer arms with good particle ID at high momenta BRAHMS: A N for charged π,K, p

RHIC Spin Overview12 April 20 th PHENIX spin physics program: ∆G, ∆q/∆q, Sivers, δq Muon ID Panels Central Arms North Muon Arm South Muon Arm Ring Imaging Cerenkov EM Calorimeter Muon Tracking Chambers Beam-Beam Counter Multiplicity/Vertex Detector Time Expansion Chamber Drift Chambers Pad Chambers Time of Flight Panels Four spectrometer arms with excellent trigger and DAQ capabilities.

RHIC Spin Overview13 April 20 th STAR spin physics program: ∆G, ∆q/∆q, Sivers, δq Large acceptance TPC and EMC -1<η<2

RHIC Spin Overview14 April 20 th 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.

Gluon Spin Distribution A LL in inclusive Jets (STAR) A LL for inclusive π 0 (PHENIX)

RHIC Spin Overview16 April 20 th  Results limited by statistical precision  Total systematic uncertainty ~0.01 (STAR) + beam pol. (RHIC)  GRSV-max gluon polarization scenario disfavored jet cone=0.4 *) Predictions: B.Jager et.al, Phys.Rev.D70(2004) A LL from Inclusive Jets in p+p Collisions at √s=200GeV J. Kiryluk, spin: Sa 9:00 STAR Preliminary STAR Projections for 2006

RHIC Spin Overview17 April 20 th Run 5 A LL (   ): 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) ¨ standard ∆G from DIS ∆G =0 max ∆G from DIS min ∆G possible Excludes large gluon spin contributions! Needs to be quantified with NLO pQCD analysis! Y. Fukao, spin: Sa 9:40 40% scale error (missing abso- lute polarization measurement). M. Liu, spin: Sa 9:20

RHIC Spin Overview18 April 20 th NLO QCD Analysis of DIS A 1 + A LL (π 0 ) M. Hirai, S. Kumano, N. Saito, hep-ph/ (Asymmetry Analysis Collaboration) DIS A 1 + A LL (π 0 ) ACC03 x M. Hirai, spin: Sa 12:10

RHIC Spin Overview19 April 20 th NLO QCD Analysis vs High p T Hadron Production in DIS DIS A 1 + A LL (π 0 ) DIS A 1 DIS A 1 + A LL (π 0 ) + neg ΔG initial High p T hadron production provides additional constraints to fit for 0.07 < x < 0.3, high p T data consistent with the three fit results for ΔG/G

RHIC Spin Overview20 April 20 th  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  s=200 GeV incl.  0 prod’n  s=500 GeV incl. jet prod’n ∆G Measurements by 2012 see Spin report to DOE

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

RHIC Spin Overview22 April 20 th QCD Cross Sections for Transverse Spin QCD: Asymmetries for transverse spin are small at high energies (Kane, Pumplin, Repko, PRL 41, 1689–1692 (1978) ) π+π+ π-π- π0π0 Suggestions: Sivers-, Collins-, Qui-Sterman, Koike mechanisms !? Experiment (E704, Fermi National Laboratory): QCD Test ! Can QCD be re-conciled with large transverse asymmetries?

RHIC Spin Overview23 April 20 th STAR: A N for backward angles from 2003 data PHENIX A N (π 0 ) and A N (π 0 ) at |η|<0.35 Phys.Rev.Lett.95:202001,2005 STAR A N (π 0 ) at 3.4<η<4.0 Phys.Rev.Lett.92:171801,2004 and (hep-ex/ ) C. Cagliardi, spin: Fr14:20 K. Tanida, spin: Fr14:40 update! Sizable asymmetries for x F > 0.4 Back angle data consistent with A N ~ 0 Updated results in parallel session!

RHIC Spin Overview24 April 20 th BRAHMS: A N for charged pions x F x 100 p T vs X F x F x 100 A N for pions:  N = [0.02] in 0.17 < x F < 0.32 in 0.17 < x F < 0.32  N = [0.015] o Expect new results from run 2005 for pions but also kaons and protons.  What can be learned by analyzing precision RHIC data on A N for different kinematics and different final state hadrons (Collins effect for kaons, protons)? J.H. Lee, spin: Fr15:00

RHIC Spin Overview25 April 20 th Large A N : mainly two mechanisms (II) Transversity quark-distributions and Collins fragmentation Correlation between proton- und quark-spin and spin dependent fragmentation (I) Sivers quark and gluon distributions Correlation between proton-spin and transverse quark momentum M. Anselmino, M. Boglione, U. D’Alesio, E. Leader, S. Melis and F. Murgia hep-ph/ quark-Sivers gluon-Sivers Transverstiy x Collins

RHIC Spin Overview26 April 20 th D. Boer and W. Vogelsang, Phys.Rev. D 69 (2004) Back-to-back di-Jets: Access to Gluon Sivers Function Current measurements should be sensitive at the level of predictions 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 PHENIX: measurement of back-to-back di-hadrons.

RHIC Spin Overview27 April 20 th Measurement of Transverse Parton Distributions at RHIC A N yes, very good A N (back-to-back) good (Sivers signature!) A T (Collins FF in jets) fair A T (Interference FF) fair A TT (Jets) systematics limited A T (Drell Yan) A TT ( Drell Yan) Direct photons (A N,A T (CFF, IFF)) RHIC by 2009 at 200 GeV ∫Ldt ~275pb -1 delivered ∫Ldt ~100pb -1 accepted (eg. PHENIX: vertex cut, trigger efficiencies, duty factor)  ∫Ldt ~25 pb -1 transverse RHIC II luminosity sufficient?

RHIC Spin Overview28 April 20 th Collins Function Measurement in e+e- at Belle       2-hadron inclusive transverse momentum dependent cross section:  e + e - CMS frame: e-e- e+e+ R. Seidl, spin: Th 17:30

RHIC Spin Overview29 April 20 th LO-QCD Analysis of HERMES and Belle Results (Efremov, Goeke, Schweitzer, hep-ph/ ) BELLE PRELIMINARY HERMES PRELIMINARY Combined fit to Hermes asymmetries (Transversity x Collins-FF) and Belle asymmetries (Collins-FF 2 )  Excellent agreement!

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

RHIC Spin Overview31 April 20 th 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 Overview32 April 20 th 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 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 Overview33 April 20 th Physics vs Luminosity and Polarization at RHIC … (RHIC II) 10 pb -1 ……………………………………  275pb -1 …….. 950pb -1 √s= ……………………… GeV ………………… GeV| P= …………………………………… Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics direct photons bottom physics W-physics A LL (hadrons, Jets)A LL (charm) A LL (γ) AL(W)AL(W) L= 1x10 31 cm -2 s -1 6x10 31 cm -2 s x10 32 cm -2 s -1 see Spin report to DOE 500GeV

RHIC Spin Overview34 April 20 th Carbon CNI Polarimeter in the AGS: Polarization during Acceleration raw asymmetry = A N  P B G  = 1.91 E beam intrinsic: G  = imperfection: G  = n each point = 50 MeV step 48- red line: simulation of polarization losses assuming constant A N

RHIC Spin Overview35 April 20 th Run 04+05: The Polarized Jet Target for RHIC Polarized Hydrogen Gas Jet Target thickness of > p/cm 2 polarization > 92.4% (+/-2)%! no depolarization from beam wake fields Silicon recoil spectrometer to measure The left-right asymmetry A N in pp elastic scattering in the CNI region to  A N < accuracy. Transfer this to the beam polarization Calibrate the p-Carbon polarimeters 2004 analysis P b = 0.39+/-0.03 Courtesy Sandro Bravar, and Yousef Makdisi

RHIC Spin Overview36 April 20 th Jet Profile and TOF vs Energy Hor. pos. of Jet cts. = 2.5 mm Number of elastic pp events FWHM ~ 6 mm as designed recoil protons unambiguously identified ! CNI peak A N 1 < E REC < 2 MeV prompt events and beam-gas  source calibration recoil protons elastic pp  pp scattering background 118 cts. subtracted JET Profile: measured selecting pp elastic events ToF vs E REC correlation T kin = ½ M R (dist/ToF) 2  ToF <  8 ns T Kin [MeV]

RHIC Spin Overview37 April 20 th Bunch shuffle Randomly reassign helicity for each fill and recalculate asymmetry. Do 1000 times and look at   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 1<pT<2 GeV/c 2<pT<3 GeV/c 3<pT<4 GeV/c 4<pT<5 GeV/c

RHIC Spin Overview38 April 20 th Run5  0 Cross Section Consistent with previous PHENIX results from runs 3+4 Extends previous results to p T of 20 GeV/c. Theory is consistent with data over nine orders of magnitude.  preliminary  0 cross section vs perturbative QCD (W. Vogelsang)  Data – Theory)/Theory