1. 3D parton structure, INT1 Overview of Transverse Single Spin Asymmetry Measurements at RHIC L.C. Bland Brookhaven National Laboratory INT Workshop on 3D parton structure of the nucleon Seattle, September 2009 Outline Review of Findings on Transverse SSA at RHIC Motivations/goals and methods Findings from the first polarized proton collisions at RHIC (medieval times) Findings from the renaissance First findings from the modern age Possible paths forward (more on Friday)

2. 3D parton structure, INT2 In QCD: proton is not just 3 quarks ! Rich structure of quarks anti-quarks, gluons Recall: simple quark model RHIC Spin Goals - I How is the proton built from its known quark and gluon constituents? As with atomic and nuclear structure, this is an evolving understanding

3. 3D parton structure, INT3 RHIC Spin Goals - II Understanding the Origin of Proton Spin Spin Sum Rules Longitudinal Spin Transverse Spin PRD 70 (2004) 114001 Understanding the origin of proton spin helps to understand its structure

4. 3D parton structure, INT4 RHIC Spin Goals - III Objectives Determination of polarized gluon distribution (  G) using multiple probes Determination of flavor identified anti-quark polarization using parity violating production of W  Transverse spin: connections to partonic orbital angular momentum (L y ) and transversity (  )

5. gluon quark pion or jet quark RHIC Spin Probes - I Polarized proton collisions / hard scattering probes of  G Describe p+p particle production at RHIC energies (  s  62 GeV) using perturbative QCD at Next to Leading Order, relying on universal parton distribution functions and fragmentation functions

6. 3D parton structure, INT6 p + p,  s = 200 GeV jets direct  PRL 97 (2006) 252001 PRL 98 (2007) 012002 p + p    + X,  s = 200 GeV PRD 76 (2007) 051106 PRL 92 (2004) 171801 Large rapidity ,K,p cross sections for p+p,  s=200 GeV PRL 98 (2007) 252001 Good agreement between experiment and theory  calibrated hard scattering probes of proton spin RHIC Spin Probes - II Unpolarized cross sections as benchmarks and heavy-ion references

7. 3D parton structure, INT7 Longitudinal Two-Spin (A LL ) Status of probing for gluon polarization via measurements of A LL for midrapidity jet,    production

8. 3D parton structure, INT8 A LL :  0 PRL 103 (2009) 012003

9. 3D parton structure, INT9 Inclusive A LL jets Results STAR B. Jager et.al, Phys.Rev.D70, 034010  The inclusive measurements give sensitivity to gluon polarization over a broad momentum range  Data are compared to predictions within the GRSV framework with several input values of  G. GRSV-std arXiv:0805.3004

10. 3D parton structure, INT10 Global Analysis Determining  g from Existing World Data PRL 101 (2008) 072001  g(x,Q 2 ) is small in the accessible range of momentum fraction [presently measured]

11. 3D parton structure, INT11 RHIC as a Polarized Proton Collider

12. 3D parton structure, INT12   A N measurements initially motivated by search for local polarimeter

13. 3D parton structure, INT13 Transverse Single-Spin Asymmetries (A N ) Probing for (1) orbital motion within transversely polarized protons; (2) Evidence of transversely polarized quarks in polarized protons. Analyzing power is a tool to measure polarization and is one example of transverse single spin asymmetries (SSA) with origins yet to be fully understood

14. 3D parton structure, INT14 Expectations from Theory What would we see from this gedanken experiment? F  0 as m q  0 in vector gauge theories, so A N ~ m q / p T or, A N ~ 0.001 for p T ~ 2 GeV/c Kane, Pumplin and Repko PRL 41 (1978) 1689

15. 3D parton structure, INT15  s=20 GeV, p T =0.5-2.0 GeV/c   0 – E704, PLB261 (1991) 201.   +/- - E704, PLB264 (1991) 462. QCD theory expects very small (A N ~10 -3 ) transverse SSA for particles produced by hard scattering. A Brief History… The FermiLab E-704 experiment found strikingly large transverse single- spin effects in p  +p fixed-target collisions with 200 GeV polarized proton beam (  s = 20 GeV).

16. 3D parton structure, INT16 STAR Large acceptance near midrapidity Windows to large rapidity

17. 3D parton structure, INT17 PHENIX Detector BBC ZDC EMCal    detection Electromagnetic Calorimeter (PbSc/PbGl): High p T photon trigger to collect  0 's,  ’s,  ’s Acceptance: |  |  x  High granularity (~10*10mrad 2 )     Drift Chamber (DC) for Charged Tracks Ring Imaging Cherenkov Detector (RICH) High p T charged pions (p T >4.7 GeV). Relative Luminosity Beam Beam Counter (BBC) Acceptance: 3.0<  3.9 Zero Degree Calorimeter (ZDC) Acceptance: ±2 mrad Local Polarimetry ZDC Shower Maximum Detector (SMD)

18. 3D parton structure, INT18 BRAHMS

19. 3D parton structure, INT19 Brahms Transvers beam pol Particle ID BRAHMS measured A N  s=62.4 GeV and 200 GeV Large xF dependent SSAs seen for pions and kaons Collinear factorization and (NLO) pQCD describe unpolarized cross-section at RHIC in wide kinematic region

20. 3D parton structure, INT20 Medieval Times First polarized p+p collisions at RHIC

21. 3D parton structure, INT21 Transverse Spin Asymmetries at Midrapidity p  +p    /h ± + X,  s = 200 GeV Transverse single spin asymmetries are consistent with zero at midrapidity PRL 95 (2005) 202001

22. 3D parton structure, INT22 Measuring A N : Inclusive  0 Production PRL 92, 171801 ( 2004 ) PRL 97, 152302 (2006) Cross-section is consistent with NLO pQCD calculations Transverse spin asymmetries found at lower √s persist to √s=200 GeV p  +p   +X, √s=200 GeV, = 3.8 RHIC Runs 2-3 with Forward Pion Detector (FPD) STAR

23. 3D parton structure, INT23 STAR-Forward Cross Sections Similar to ISR analysis J. Singh, et al Nucl. Phys. B140 (1978) 189. Expect QCD scaling of form:  Require  s dependence (e.g., measure   cross sections at  s = 500 GeV) to disentangle p T and x T dependence

24. 3D parton structure, INT24 The Renaissance

25. 3D parton structure, INT25 Idea: directly measure k T by observing momentum imbalance of a pair of jets produced in p+p collision and attempt to measure if k T is correlated with incoming proton spin Boer & Vogelsang, PRD 69 (2004) 094025 jet A N  p beam  ( k T  S T ) p beam into page STAR Results vs. Di-Jet Pseudorapidity Sum Run-6 Result STAR PRL 99 (2007) 142003 Emphasizes (50%+ ) quark Sivers A N consistent with zero  ~order of magnitude smaller in pp  di-jets than in semi-inclusive DIS quark Sivers asymmetry! VY 1, VY 2 are calculations by Vogelsang & Yuan, PRD 72 (2005) 054028

26. 3D parton structure, INT26 x F Dependence of Inclusive  0 A N RHIC Run 6 with FPD++ Fits to SIDIS (HERMES) is consistent with data A N at positive x F grows with increasing x F PRL 101, 222001 ( 2008 ) arXiv:0801.2990v1 [hep-ex] U. D’Alesio, F. Murgia Phys. Rev. D 70, 074009 (2004) arXiv:hep-ph/0712.4240 C. Kouvaris, J. Qiu, W. Vogelsang, F. Yuan, Phys. Rev. D 74, 114013 (2006). STAR

27. 3D parton structure, INT27 x F dependence is consistent with Sivers model Rising p T dependence is not explained 6/1/200927Chris Perkins STAR, PRL 101 (2008) 222001 RHIC Runs 3,5,6 with FPD p T Dependence of Inclusive  0 A N B.I. Abelev et al. (STAR) PRL 101 (2008) 222001 STAR

28. 3D parton structure, INT28 x F and p T dependence of A N for p  +p  ± +X,  s=62 GeV A N (  +) ~ -A N (  - ), consistent with results at lower  s and u,d valence differences At fixed x F, evidence that A N grows with p T I. Arsene, et al. PRL101 (2008) 042001

29. 3D parton structure, INT29 Transverse Spin Effects for Kaons I. Arsene, et al. PRL101 (2008) 042001 p  +p  K ± +X,  s=62 GeV Large transverse single spin asymmetries are observed for kaons

30. 3D parton structure, INT30 PHENIX Muon Piston Calorimeter SOUTH 192 PbWO4 crystals with APD readout Better than 80% of the acceptance is okay 2.2  2.2  18 cm 3

31. 3D parton structure, INT31 PHENIX Goes Forward First results with muon piston calorimeter from run 6 p  +p   +X,  s = 62 GeV Transverse SSA persists with similar characteristics over a broad range of collision energy (20 <  s < 200 GeV)

32. 3D parton structure, INT32 STAR 2006 PRELIMINARY Heavier mesons also accessible at high X F Di-photons in FPD with E(pair)>40 GeV No “center cut” (requirement that two-photon system point at middle of an FPD module) With center cut and Z  <0.85 Average Yellow Beam Polarization=56% arXiv:0905.2840 ( S. Heppelmann, PANIC 2008)

33. 3D parton structure, INT33 Towards Modern Times To separate Sivers and Collins effects need to move beyond inclusive production To isolate Sivers effect, need to either avoid fragmentation or integrate azimuthally Full Jets, Di-Jets (away side), Direct photons, Drell-Yan To isolate Collins effect, need to look azimuthally within a jet.

34. 3D parton structure, INT34 Guzey, Strikman and Vogelsang Phys. Lett. B603 (2004) 173 PYTHIA Simulation constrain x value of gluon probed by high- x quark by detection of second hadron serving as jet surrogate. span broad pseudorapidity range (-1<  <+4) for second hadron  span broad range of x gluon provide sensitivity to higher p T for forward    reduce 2  3 (inelastic) parton process contributions thereby reducing uncorrelated background in  correlation.

35. 1 Brookhaven National Laboratory 2 University of California- Berkeley 3 Pennsylvania State University 4 IHEP, Protvino 5 Stony Brook University 6 Texas A&M University 7 Utrecht, the Netherlands 8 Zagreb University STAR Forward Calorimeter Projects F.Bieser 2, L.Bland 1, E. Braidot 7, R.Brown 1, H.Crawford 2, A.Derevshchikov 4, J.Drachenberg 6, J.Engelage 2, L.Eun 3, M.Evans 3, D.Fein 3, C.Gagliardi 6, A. Gordon 1, S.Hepplemann 3, E.Judd 2, V.Kravtsov 4, J. Langdon 5, Yu.Matulenko 4, A.Meschanin 4, C.Miller 5, N. Mineav 4, A. Mischke 7, D.Morozov 4, M.Ng 2, L.Nogach 4, S.Nurushev 4, A.Ogawa 1, H. Okada 1, J. Palmatier 3, T.Peitzmann 7, S. Perez 5, C.Perkins 2, M.Planinic 8, N.Poljak 8, G.Rakness 1,3, J. Tatarowicz 3, A.Vasiliev 4, N.Zachariou 5 These people built the Forward Meson Spectrometer (FMS) and/or its components

36. 3D parton structure, INT36 STAR Forward Meson Spectrometer PRL 101 (2008) 222001 50  larger acceptance than the run-3 forward pion detector (FPD).  azimuth for 2.5<  <4.0 Discriminate single  from    up to ~60 GeV Runs 3-6 FPD Run 8 FMS North half of FMS before closing

37. 3D parton structure, INT37 Run-8 Results from STAR Forward Meson Spectrometer (FMS) Full azimuth spanned with nearly contiguous electromagnetic calorimetry from -1<  <4  approaching full acceptance detector

38. 3D parton structure, INT38 Run 8 FMS Inclusive  0 Results Octant subdivision of FMS for inclusive   spin sorting. arXiv:0901.2828 Nikola Poljak – SPIN08 Azimuthal dependence as expected A N comparable to prior measurements x y P

39. 3D parton structure, INT39 Negative x F arXiv:0901.2763 (J. Drachenberg– SPIN08) Akio Ogawa – CIPANP 09 Positive x F RHIC Run 8 with East FPD/FMS p T Dependence Indication of Positive A N persists up to p T ~5 GeV Needs more transverse spin running Negative x F consistent with zero

40. 3D parton structure, INT40 First Look at “Jet-like” Events in the FMS Event selection: “Jet shape” in data matches simulation well Reconstructed Mass doesn’t match as well High-Tower Trigger used in Run 8 biases Jets >15 detectors with energy > 0.4GeV in the event (no single pions in the event) cone radius = 0.5 (eta-phi space) “Jet-like” p T > 1 GeV/c ; x F > 0.2 2 perimeter fiducial volume cut (small/large cells) “Jet-shape” distribution of energy within jet- like objects in the FMS as a function of distance from the jet axis. arXiv:0901.2828 (Nikola Poljak – SPIN08)

41. 3D parton structure, INT41 Comparison to dAu Spin-1 meson A N High x F Vector Mesons RHIC Run 8 with FMS Background only MC Run8 FMS data Fit is gaussian + P3 μ=0.784±0.008 GeV σ=0.087±0.009 GeV Scale=1339±135 Events 3 photon events to look for  0   BR  P T (triplet)>2.5 GeV/c E(triplet)>30 GeV P T (photon cluster)>1.5 GeV/c P T (π 0 )>1 GeV/c Significant (10  )  0  signal seen in the data. arXiv:0906.2332 A Gordon– Moriond09 Triple Photons :  0  Next :

42. 3D parton structure, INT42 STAR Detector Large rapidity coverage for electromagnetic calorimetry (-1<  <+4) spanning full azimuth  azimuthal correlations Run-8 was the first run for the Forward Meson Spectrometer (FMS)

43. 3D parton structure, INT43 Azimuthal Correlations with Large  E. Braidot (for STAR), Quark Matter 2009 Uncorrected Coincidence Probability (radian -1 ) p+p   +h ± +X,  s=200 GeV   requirements: p T,  >2.5 GeV/c 2.8<   <3.8 h ± requirements: 1.5<p T,h <p T,   h  <0.9 clear back-to-back peak observed, as expected for partonic 2  2 processes fixed and large  trigger, with variable  h  map out Bjorken- x dependence of greatest interest for forward direct-  trigger

44. 3D parton structure, INT44 Forward  0 – Forward  0 Azimuthal Correlations Possible back-to-back di-jet/di-hadron Sivers measurement Possible near-side hadron correlation for Collins fragmentation function/Interference fragmentation function + Transversity Low-x / gluon saturation study – accessing lowest x Bj gluon Akio Ogawa- CIPANP 09

45. 3D parton structure, INT45 Proposals for the Future SSA beyond inclusive meson production Forward jets Forward photons Forward virtual photons (Just mentioned here… much more about future prospects on Friday)

46. 3D parton structure, INT46 Conclusions and Summary Transverse spin asymmetries are present at RHIC energies Transverse spin asymmetries are present at large  Particle production cross sections and correlations are consistent with pQCD expectations at large  where transverse spin effects are observed Essential to go beyond inclusive production to disentangle dynamical origins