RHIC Spin Physics M Grosse Perdekamp University of

RHIC Spin Physics • • M. Grosse Perdekamp University of Illinois and RBRC • 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 BGM Workshop on Deep Inelastic Scattering, April 20 -24, 2006 , Tsukuba, Japan April International 20 th

RHIC five complementary experiments RHIC: ion-ion and polarized p-p Collider pp 2 pp April 20 th RHIC Spin Overview 2

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 Ge. V) o Proton Spin Structure polarized proton-proton collisions (p-p: √s=200 to 500 Ge. V) o Low-x and high parton densities ion-deuteron collisions (d-Au: √s. NN=200 Ge. V) C. Cagliardi low-x: Sat. 11. 10 very active field: eg. 74 PRL letters in the first 5 years April 20 th RHIC Spin Overview 3

Proton Spin Structure in Polarized p-p Collisions at RHIC goals available channels determine first moment of the spin dependent gluon distribution. jets, hadrons, photon-jet, heavy flavor separation of quark and anti-quark spin distributions Single spin lepton asymmetries in W-production measurement of transversity and Sivers distributions April 20 th RHIC Spin Overview (1) AN (2) ATT in Collins- and Interference-Fragmentation (3) ATT and AT In Drell Yan 4

Access to Parton Distributions at RHIC Measure: (spin dependent) cross sections QCD analysis: (spin dependent) distribution functions April 20 th RHIC Spin Overview 5

Example: G(x) from a global NLO p. QCD analysis with projected future direct photon data from PHENIX Does NLO p. QCD 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) April 20 th RHIC Spin Overview 6

Inclusive Hadron Cross Sections vs NLO QCD PHENIX π0 cross section a |η|<0. 35 Phys. Rev. Lett. 91: 241803, 2003 April 20 th RHIC Spin Overview STAR π0 cross section a 3. 4<η<4. 0 Phys. Rev. Lett. 92: 171801, 2004 7

Direct Photons and Inclusive Jets vs NLO p. QCD Inclusive Jet Cross section Direct Photon Cross section PHENIX Preliminary M. Miller, hadronic final states: Sat. 14. 20 Good agreement between NLO p. QCD calculations and experiment at RHIC ! Use NLO p. QCD analysis to extract Theory show good (spin dependent) quark and calculation gluon STAR Preliminary agreement distributions from RHIC data! with the experimental cross section. Theory perspective: April 20 th RHIC Spin Overview M. Stratmann, spin: Fr 16: 30 8

A novel experimental method: method Probing Proton Spin Structure Through High Energy Polarized p-p Collisions Absolute Polarimeter (H jet) Siberian Snakes RHIC p. C Polarimeters A. Bravar, BRAHMS PHOBOS spin: Fr 16: 10 & PP 2 PP Siberian Snakes 2005 Complete! helical magnets high current polarized source high energydipoles proton polarimetry Spin Flipper PHENIX Spin Rotators STAR Partial Snake Strong Snake Polarized Source LINAC 200 Me. V Polarimeter Last Week at RHIC BOOSTER peak Helical Partial Snake AGS L 2. 5 P 67% average design 1. 2 61% 6. 0 70% Luminosity in 1031 cm-2 s-1 Rf Dipole AGS Polarimeter Generous support from RIKEN, Japan and DOE

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) F. Simon, spin: Sa 10: 20 (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. April 20 th RHIC Spin Overview 10

BRAHMS: AN for charged π, K, p 100% transverse spin! Two spectrometer arms with good particle ID at high momenta April 20 th RHIC Spin Overview 11

PHENIX spin physics program: ∆G, ∆q/∆q, Sivers, δq EM Calorimeter Time Expansion Chamber Beam-Beam Counter Muon Tracking Chambers Central Arms Muon ID Panels Pad Chambers Multiplicity/Vertex Detector Drift Chambers North Muon Arm South Muon Arm Time of Flight Panels Four spectrometer arms with excellent trigger and DAQ capabilities. April 20 th Ring Imaging Cerenkov RHIC Spin Overview 12

STAR spin physics program: ∆G, ∆q/∆q, Sivers, δq Large acceptance TPC and EMC -1<η<2 April 20 th RHIC Spin Overview 13

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. April 20 th RHIC Spin Overview 14

Gluon Spin Distribution ALL in inclusive Jets (STAR) ALL for inclusive π0 (PHENIX) April 20 th RHIC Spin Overview 15

ALL from Inclusive Jets in p+p Collisions at √s=200 Ge. V jet cone=0. 4 STAR Preliminary STAR Projections for 2006 *) Predictions: B. Jager et. al, Phys. Rev. D 70(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 April 20 th RHIC Spin Overview 16

Run 5 ALL(p 0): 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 S m G fro DI x∆ a m sible G pos min ∆ m DIS ro d ∆G f r a d n a st Excludes large gluon spin contributions! Needs to be quantified with NLO p. QCD analysis! ∆G =0 40% scale error (missing absolute polarization measurement). ¨ April 20 th RHIC Spin Overview 17

NLO QCD Analysis of DIS A 1 + ALL(π0) M. Hirai, S. Kumano, N. Saito, hep-ph/0603212 (Asymmetry Analysis Collaboration) M. Hirai, spin: Sa 12: 10 DIS A 1 + ALL(π0) ACC 03 x April 20 th RHIC Spin Overview 18

NLO QCD Analysis vs High p. T Hadron Production in DIS 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 DIS A 1 + ALL(π0) + neg ΔGinitial April 20 th RHIC Spin Overview 19

∆G Measurements by 2012 see Spin report to DOE http: //spin. riken. bnl. gov/rsc/ s=200 Ge. V incl. 0 prod’n s=500 Ge. V 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 April 20 th RHIC Spin Overview 20

C. Cagliardi, Transverse Spin AN for inclusive hadrons (BRAHMS, PHENIX, STAR) spin: Fr 14: 20 K. Tanida, spin: Fr 14: 40 J. H. Lee, spin: Fr 15: 00 April 20 th RHIC Spin Overview 21

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 (E 704, Fermi National Laboratory): π+ QCD Test ! π0 πCan QCD be Sivers-, re-conciled with Suggestions: Collins-, Qui-Sterman, Koike mechanisms !? large transverse asymmetries? April 20 th RHIC Spin Overview 22

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 K. Tanida, Phys. Rev. Lett. 92: 171801, 2004 and (hep-ex/0502040) spin: Fr 14: 40 C. Cagliardi, spin: Fr 14: 20 update! • • • Sizable asymmetries for x. F > 0. 4 Back angle data consistent with AN ~ 0 Updated results in parallel session! April 20 th RHIC Spin Overview 23

BRAHMS: AN for charged pions J. H. Lee, spin: Fr 15: 00 AN for pions: AN = +0. 05 +- 0. 005 +- [0. 015] p. T vs XF AN = -0. 08 +- 0. 005 +- [0. 02] in 0. 17 < x. F < 0. 32 x. F x 100 o Expect new results from run 2005 for pions but also kaons and protons. x. F x 100 April 20 th What can be learned by analyzing precision RHIC data on AN for different kinematics and different final state hadrons (Collins effect for kaons, protons)? RHIC Spin Overview 24

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 rk- Siv ers Correlation between proton-spin and transverse quark momentum qua (II) Transversity quark-distributions and Collins fragmentation Correlation between proton- und quark-spin and spin dependent fragmentation gluon-Sivers April 20 th RHIC Spin Overview Transverstiy x Collins 25

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 Ge. V trigger jet > 4 Ge. V away side jet D. Boer and W. Vogelsang, Phys. Rev. D 69 (2004) 094025 Current measurements should be sensitive at the level of predictions PHENIX: measurement of back-to-back di-hadrons. April 20 th RHIC Spin Overview 26

Measurement of Transverse Parton Distributions at RHIC luminosity sufficient? AN yes, very good RHIC by 2009 at 200 Ge. V AN(back-to-back) good (Sivers signature!) ∫Ldt ~275 pb-1 delivered AT (Collins FF in jets) fair AT (Interference FF) fair ∫Ldt ~100 pb-1 accepted (eg. PHENIX: vertex cut, trigger efficiencies, duty factor) ATT (Jets) systematics limited ∫Ldt ~25 pb-1 transverse AT (Drell Yan) Direct photons (AN, AT(CFF, IFF)) April 20 th RHIC II ATT( Drell Yan) RHIC Spin Overview 27

Collins Function Measurement in e+e- at Belle e+e- CMS frame: R. Seidl, spin: Th 17: 30 j 2 -p e. Q j 1 j 2 e+ 2 -hadron inclusive transverse momentum dependent cross section: April 20 th RHIC Spin Overview 28

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-FF 2) Excellent agreement! April 20 th RHIC Spin Overview 29

Plans for the measurement of spin dependent quark and anti-quark in W-production at RHIC April 20 th RHIC Spin Overview 30

Projected Sensitivities in PHENIX Ø Machine and detector requirements: – ∫Ldt=800 pb-1, P=0. 7 at √s=500 Ge. V – required upgrades: high rate muon trigger (PHENIX) high momentum tracking (STAR) 2009 to 2012 running at √s=500 Ge. V is projected to yield ∫Ldt ~950 pb-1 April 20 th RHIC Spin Overview 31

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. April 20 th RHIC Spin Overview 32

Physics vs Luminosity and Polarization at RHIC see Spin report to DOE http: //spin. riken. bnl. gov/rsc/ L= 1 x 1031 cm-2 s-1 P= 0. 5 0. 6 6 x 10 31 cm-2 s-1 1. 6 x 1032 cm-2 s-1 0. 7 ………………… √s= ……………. . 200 Ge. V …………………. . 500 Ge. V| 2005 2006 2007 2008 2009 10 pb-1 ………………… 275 pb-1 @ 200 Ge. V …. 2012 (RHIC II) ……. . 950 pb-1 @ 500 Ge. V Inclusive hadrons + Jets ~ 25% Transverse Physics Charm Physics ALL(hadrons, Jets) ALL(charm) direct photons bottom physics W-physics ALL(γ) April 20 th RHIC Spin Overview AL(W) 33

Carbon CNI Polarimeter in the AGS: Polarization during Acceleration raw asymmetry = AN · PB each point = 50 Me. V step intrinsic: Gg =12+n imperfection: Gg = n April 20 th 36 -n Gg = 1. 91 Ebeam 48 -n 36+n red line: simulation of polarization losses assuming constant AN RHIC Spin Overview 34

Run 04+05: The Polarized Jet Target for RHIC Courtesy Sandro Bravar, and Yousef Makdisi Polarized Hydrogen Gas Jet Target thickness of > 1012 p/cm 2 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 April 20 th RHIC Spin Overview 35

Number of elastic pp events Jet Profile and TOF vs Energy recoil protons elastic pp pp scattering JET Profile: measured selecting pp elastic events FWHM ~ 6 mm as designed background 118 cts. subtracted To. F < ± 8 ns T Kin [Me. V] Hor. pos. of Jet 10000 cts. = 2. 5 mm CNI peak AN 1 < E REC < 2 Me. V prompt events and beam-gas • recoil protons unambiguously identified ! April 20 th RHIC Spin Overview source calibration To. F vs EREC correlation Tkin= ½ MR(dist/To. F)2 36

Bunch shuffle • • Randomly reassign helicity for each fill and recalculate asymmetry. Do 1000 times and look at c 2 distribution. Agree with expected distribution Bunch to bunch systematics smaller than current statistics. April 20 th 1<p. T<2 Ge. V/c 2<p. T<3 Ge. V/c 3<p. T<4 Ge. V/c 4<p. T<5 Ge. V/c 5<p. T<6 Ge. V/c 6<p. T<7 Ge. V/c 7<p. T<8 Ge. V/c 8<p. T<9 Ge. V/c RHIC Spin Overview 37

Run 5 p 0 Cross Section • Consistent with previous PHENIX results from runs 3+4 2005 preliminary p 0 cross section vs perturbative QCD (W. Vogelsang) • Extends previous results to p. T of 20 Ge. V/c. • Theory is consistent with data over nine orders of magnitude. (Data – Theory)/Theory April 20 th RHIC Spin Overview 38