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Current and Future Transverse Spin at the PHENIX Experiment at RHIC

Current and Future Transverse Spin at the PHENIX Experiment at RHIC. Yousef I. Makdisi Brookhaven National Laboratory For The PHENIX Collaboration. Outline. A brief experimental review of transverse asymmetries: A symmetries at Large X T Asymmetries near X F = 0

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Current and Future Transverse Spin at the PHENIX Experiment at RHIC

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  1. Current and Future Transverse Spin at the PHENIX Experiment at RHIC Yousef I. Makdisi Brookhaven National Laboratory For The PHENIX Collaboration

  2. Outline • A brief experimental review of transverse asymmetries: • A symmetries at Large XT • Asymmetries near XF = 0 • Asymmetries at Large XF • Transverse asymmetry measurement in PHENIX at XF= 0 • Near Term upgrades and transverse physics reach • Longer term upgrades and physics reach • Summery and outlook

  3. Asymmetry in inclusive production at Large XT + 0 0 Polarized Beam - Polarized Target Polarized Target - p(d) 0 x @ 40 GeV/c V.D. Apokin et al., Phys.Lett.B243:461-464,1990 p J. Antille et al. Phys.Lett.B94:523,1980 S. Saroff et al. PRL64,995,1990 Large Asymmetries in + and 0 production No asymmetry in - and proton production

  4. Asymmetry near XF = 0 D.L. Adams et al. PRD53:4747-4755,1996 Higher s = 20 GeV are we in the partonic regime? Unlike at lower energy No asymmetry in 0 production

  5. Asymmetry in pion production at large XF • ZGS (12 GeV)AGS (22 GeV) FNAL (200 GeV) Phys.Rev.D65:092008,2002 Phys. Lett. B261(1991)201 Phys. Lett. B264(1991)462 Large asymmetry in pion production Asymmetry persists to high energy No asymmetry in proton production at the AGS (not shown)

  6. What should one expect at RHIC energies? Predictions by different theorists expect non-zero AN values, attributed to different dynamics, to persist at RHIC energies: s=200 GeV... 0.15 p+ Simulation w/Pb=50% and 1.5pb-1 p0 0.05 AN p- -0.05 PRL 92 (2004) 171801 Collins effect Anselmino, et al. PRD 60 (1999) 054027. -0.15 0.4 Sivers effect Anselmino, et al. Phys. Lett. B442 (1998) 470. E(GeV) 0.2 Twist 3 effectQiu and Sterman, Phys. Rev. D59 (1998) 014004. 0 -0.2 0 0.2 0.4 0.6 0.8 XF PRL92(2004) 171801

  7. What have we learned so far? • At large XF asymmetries persist from low to highest energy measured. • At large XT asymmetry is seen in + and 0 but not in - • Single Spin asymmetry is zero near XF = 0 (not large XT) • Sivers and Collins effects apply at low and high energy • Are we observing partonic effects: • polarized valence quark interactions at large XF • Polarized valence quark interactions at large XT • polarized gluon interaction at XF = 0 and low pt • polarized quark-gluon interactions at higher pt • Or possibly an XR effect? • The PHENIX data will probe the gluon-gluon • and quark- gluon domain. S. Saroff et al. PRL64,995,1990

  8. The Phenix Detector for Run 2 Central arms Photons, electrons, identified charged hadrons |h| < 0.35 Df = 180 degrees Forward muon arms Track and identify muons 1.2 < |h| < 2.4 Df = 2p Detector fully operational

  9. Midrapidity 0 and charged hadron Production in Proton-Proton Collisions at s = 200 GeV NLO pQCD W. Vogelsang et al. CTEQ6M PDF KKP FF =2pT, pT, 1/2pT PHENIX Preliminary • Results consistent with pQCD calculations and favors a larger gluon-to-pion FF (KKP) • Provides confidence to use NLO pQCD analysis to extract spin dependent pdfs. via hadronic channels Phys. Rev. Lett. 91, 241803, 2003

  10. AN in inclusive charged hadron and 0 production • Data were collected in the first polarized proton run at RHIC “Run 2” with 0.15 pb-1. The accelerator ran with vertical polarization only. • An overall minimum bias trigger was employed using the BBC counters. These counters were also used as relative luminosity monitors between bunches of opposite polarization. • The EMC photon trigger with an energy threshold @ 0.8 GeV was used to enhance the neutral pion sample. • The two-photon pizero mass cut was from 0.12 - 0.16 GeV. The Background contribution ranged from 58%-9% from low to high pt and the contribution to the asymmetry was estimated from looking at the both sides of the peak. • Required no hits in the RICH counter to eliminate electrons < 1% in the charged hadrons sample. No cuts on decays from long lived particles.

  11. Inclusive pions analysis cont’dC. Aidala • Calculate asymmetry of (signal + background 50 Mev around the peak) in the p0 mass window • Calculate the asymmetry of two different background regions • Subtract the asymmetries • .

  12. Systematics F. Bauer and K. Okada • comparison of independent measurement for two polarized beams • both beams (“blue” and “yellow”) polarized • comparison of independent measurement for left and right detectors • comparison of minimum-bias and high-pT triggered data samples • store-by-store consistency of asymmetry values • “bunch shuffling” • randomly reassign the polarization direction for each bunch crossing • recalculate the asymmetry • repeat many times to produce a shuffled asymmetry distribution centered around zero • compare width of “shuffled” distribution to statistical error on the physics asymmetry

  13. qg gg qq AN in inclusive hadron and pi zero productionC. Aidala and K. Okada Mainly sensitive to g-g and g-q interactions Data taken 0.15 pb-1 and 15 % beam polarization AN is consistent with zero The difference in pT reach is due to triggering

  14. preliminary AN = 0.110±0.015 AN = 0.108±0.0087 preliminary AN in inclusive forward neutron production AN ~ -12% xF > 0.2 pT < 0.3 GeV/c A possible diffractive process

  15. AN in inclusive hadron production-near term  - production • An aerogel counter was installed to provide PID to 8 GeV/c. For pions above 4 GeV the RICH provides a trigger. • At ~1 pb-1/week(2006?) with vertical beam polarization one could extend the pt reach to the quark-gluon contribution • We will attempt to measure the Sivers kT effect using back-to-back leading hadrons. Boer and Vogelsang hep-ph/0312320

  16. Transversity measurements-longer term The proposed PHENIX detector upgrades include the following: a) A silicon vertex detector with - 1   +1 b) A Hadron blind detector c) A nose cone calorimeter This will provide the capability to: a) Measure AN in 0 production at forward XF b) Efficient charged hadron trigger using the HBD/RICH and EMC c) Reconstruct back to back jets d) Allow measurement of the Collins effect using  interference. Will requires high luminosity 10 pb-1/week

  17. Summary • The polarized proton collider at RHIC provides a unique opportunity to study spin physics effects. • RUN II • With 15% beam polarization and low luminosity PHENIX measured the single spin asymmetry ANin inclusive pi zero and charged hadrons near XF=0. • The measured asymmetry is consistent with zero with good statistics. • The asymmetry is well below that measured by STAR at large XF • The measurement is quite sensitive to transverse gluon Sivers. • Future RUNS • The near term upgrades, higher luminosity and beam polarization should allow a higher pt reach 6-10 GeV/c and access the quark- gluon contribution. • Attempt a first measurement of the Sivers effect. • Longer term upgrades of PHENIX and the collider will allow a full compliment of transversity measurements

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