1. Transverse Single Spin Asymmetries at High x F in Mickey Chiu

2. 2 Transverse Proton Spin Physics quark helicity distribution – known transversity distribution – unknown gluon helicity distribution – poorly known Polarized parton distribution functions E704 Helicity violation term due to finite quark masses Naïve LO, Leading Twist, pQCD Result

3. 3 Transverse Proton Spin Physics Various possible explanations have been proposed to explain these asymmetries Transversity x Spin-dep fragmentation (e.g., Collins effect or IFF), Intrinsic-k T in proton (Transverse Momentum Dep Functions), Eg, Sivers Function Perturbative LO Twist-3 Calculations (Qiu-Sterman, Efremov, Koike) These calculations have been related to the Sivers function Or some combination of the above Caveat: The theory is still being actively worked out A Unified picture for single transverse-spin asymmetries in hard processes, Ji, Qiu, Vogelsang, Yuan PRL97:082002,2006 Anim. courtesy J. Kruhwel, JLAB

4. 4 PHENIX at RHIC Spin Run02Run05Run06Run08  s (GeV/c 2 ) 200 62.4200  Ldt (pb -1 ) 0.15 2.70.025.2 0.150.470.570.50~0.50 P2LP2L0.00340.0330.870.051.3 STAR PHENIX Transversely Polarized p+p Data Set Central Arm Tracking |  | < 0.35, x F ~ 0 Drift Chamber (DC) momentum measurement Pad Chambers (PC) pattern recognition, 3d space point Time Expansion Chamber (TEC) additional resolution at high pt Central Arm Calorimetry PbGl and PbSc Very Fine Granularity Tower  x  ~ 0.01x0.01 Trigger Central Arm Particle Id RICH electron/hadron separation TOF  /K/p identification Global Detectors (Luminosity,Trigger) BBC 3.0 < |  | < 3.9 Quartz Cherenkov Radiators ZDC/SMD (Local Polarimeter) Forward Hadron Calorimeter Forward Calorimetry 3.1 < |  | < 3.7 MPC PbWO 4 Crystal Forward Muon Arms 1.2 < |  | < 2.4 MPC

5. 5 PHENIX Muon Piston Calorimeter Upgrade Small cylindrical hole in Muon Magnet Piston, Radius 22.5 cm and Depth 43.1 cm SOUTH 2.16Refractive Index 420-440, 500 nmMain Emission Lines 1000 GyRadiation Hardness -2% /  C Temp. Coefficient ~10 p.e./MeV @ 25  C Light Yield 22.4 cmInteraction Length 0.89 cmRadiation Length 2.0 cmMoliere radius 721.3 gWeight 20 X0, 0.92 Length 2.2x2.2x18 cm 3 Size 8.28 g/cm 3 Density PbWO 4 PHD Theses J. Koster, UIUC: di-pion A LL D. Kleinjan, UCR: Transverse spin effects in p  +p B. Meredith, UIUC, K. Sedgwick, UCR, Z. Citron, SUNYSB: search for saturation of g(x) in d+Au M. Mendoza, UCR: R dA in d+Au Kwangbok Lee, Korea U:  C in p+p, d+Au

6. 6 Muon Piston Calorimeter Performance MIP Peak Background subtracted All Pairs Mixed Events Photon Pair Cuts Pair Energy > 8 GeV Asymmetry |E 1 -E 2 |/|E 1 +E 2 | < 0.6 Noisy Towers in Run06 (up to 25% of MPC) Excluded Width ~ 20 MeV Shower Reconstruction Using Shower Shape Fits Energy Scale Set by MIP In Noisy Towers, Used Tower Spectrum Confirmed with  0,  peaks

7. 7 Left Right 2. Or, take the left-right difference between 2 detectors This is susceptible to detector Relative Acceptance differences 1. Yield difference between up/down proton in a single detector This is susceptible to Rel. Luminosity differences Transverse Single Spin Asymmetries Definition: where p is the 4-momentum of a particle (hadron, jet, photon, etc...) Mostly insensitive to Relative Luminosity and Detector Acceptance differences 3. Or, take the cross geometric mean (square-root formula) Experimentally, there are a variety of (~equivalent) ways this can be measured.

8. 8 3.0<  <4.0 p  +p  0 +X at  s=62.4 GeV/c 2  0 A N at High x F PLB 603,173 (2004) process contribution to  0,  =3.3,  s=200 GeV Large asymmetries at forward x F Valence quark effect? x F, p T,  s, and  dependence provide quantitative tests for theories

9. 9 PHENIX Preliminary BRAHMS PRL 101, 042001 RHIC Forward Pion A N at 62.4 GeV Brahms Spectrometer at “2.3  ” and “3.0  ” setting  = 3.44, comparable to PHENIX all eta Qualitatively similar behavior to E704 data: pi0 is positive and between pi+ and pi-, and roughly similar magnitude: AN(pi+)/AN(pi0) ~ 25-50% Flavor dependence of identified pion asymmetries can help to distinguish between effects Kouvaris, Qiu, Vogelsang, Yuan, PRD74:114013, 2006 Twist-3 calculation for pions for pion  exactly at 3.3 Derived from fits to E704 data at  s=19.4 GeV and then extrapolated to 62.4 and 200 GeV E704, 19.4 GeV, PLB261, (1991) 201

10. 10 Comparison to  0 at  s = 200 GeV/c 2 At higher , the scaling with  s is stronger? The  dependence is switched when going from 62 to 200 GeV?  <3.5  >3.5 PHENIX 62 GeV Preliminary STAR arxiv:0801.2990v1, p+p  0 @  s=200 GeV, accepted by PRL

11. 11 Kinematic Cuts and A N eta<3.5 eta>3.5 Mean A N is measured to be lower for p T >1, even though mean x F is higher for this p T bin, and higher x F implies higher asymmetry This implies that A N is dropping with pt for a given x F slice The  cut, for a given x F slice, splits that slice into high pt and low pt, with the lower eta selecting higher pt This implies that A N at lower  should be smaller, consistent with predictions of PRD74:114013 However, at 62.4 GeV the p T are low (pQCD invalid?) Cross-section is being analyzed now Phys.Rev.D74:114013,2006.

12. 12 NLO pQCD  0 Cross-section Bourrely and Soffer, Eur.Phys.J.C36:371-374,2004 Cross-sections generally better described at mid-rapidity and at higher  s NLL calculations are very promising for intermediate to lower  s PHENIX  s=62.4 GeV y=0  0 cross-section, arXiv:0810.0701, submitted to PRDarXiv:0810.0701 Understanding lower p T A N important for understanding A N at higher  s More remarkable because A N (x F ) are similar across all

13. 13 Sivers  n from Back2Back Analysis Boer and Vogelsang, Phys.Rev.D69:094025,2004, hep-ph/0312320 Bomhof,Mulders,Vogelsang,Yuan, PRD75:074019,2007 Boer and Vogelsang find that this parton asymmetry will lead to an asymmetry in the  distribution of back-to-back jets Should also be able to see this effect with fragments of jets, and not just with fully reconstructed jets Important analysis to decouple the effects in single inclusive A N MPC  0 Cent h,  0 * See also Feng Wei’s talk in previous session 

14. 14 1-dimensional Summary Much new data coming from transversely polarized proton interactions p  +p (RHIC), but also e+p  SIDIS (Hermes, Compass, JLab), e + e - (Belle) Along with new data on the helicity distribution of partons in the proton (gluon spin), transversely polarized proton collisions could add a wealth of new information on proton structure Transversity, Orbital angular momentum? GPD’s may be cleanest way to OAM However, strongest asymmetries are in p  +p PHENIX has measured the transverse asymmetry of  0, h , and J/ , covering an x F from 0 to 0.6 (at two different collision energies). There are also sizable asymmetries from forward neutrons out to x F ~ 1. In the future, we expect ~25% of the polarized p+p running will be in the transverse mode Lots more data coming New upgrade detectors should significantly enhance physics reach Forward Calorimeter in the Nose Cone Region Silicon Detectors (SVTX and FVTX) proton wave-function

15. 15 Run08 pi0 E > 6 GeV Asymm<0.6 A LOT more data is expected from Run08 Currently the data processing is in progress at CC-Japan As of this past Tuesday it was 80% done, still needs to be transferred Results on pi0 A N to be expected by early next year There are also other possibilites from this data set…

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17. 17 NCC MPC VTX & FVTX -3 -2 -1 0 1 2 3   coverage 2  HBD EMCAL Future PHENIX Acceptance History – PHENIX is a small acceptance, high rate, rare probes (photons, J/Psi, etc.) detector Future – Add acceptance and add some new capabilities (hadron blind, displaced vertex) Muon Piston Calorimeter (2006-end): PbWO 4 Electromagnetic Calorimeter Hadron Blind Detector (2007-2009): CsI Triple GEM Cerenkov Detector Nose Cone Calorimeter (2010-end): Tungsten-Silicon Electromagnetic Calorimeter with limited Jet Capabilities (1 arm, possibly 2 with funding) SVTX (2009-end): Central Arm Silicon Tracker FVTX (2010-end): Muon Arm Silicon Tracker

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