1 / 23

Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008

Recent PHENIX results on p + , p - and h production in polarized pp collisions at RHIC at  s=200 GeV. Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008 April 7-11, London, UK. Spin Sum Rule: The latest…. DSSV, arXiv: 0804.0422

finn
Download Presentation

Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent PHENIX results on p+, p- and h production in polarized pp collisions at RHIC at s=200 GeV Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008 April 7-11, London, UK

  2. Spin Sum Rule: The latest… DSSV, arXiv: 0804.0422 First “global” (DIS+SIDIS+pp) analysis! HERMES, arXiv: 0802.2499 DG small in measured range. Gluon orbital momentum? Contribution at small or large x? Gluons carry half the momentum. Do they carry half the spin? PHENIX p0 (large gg contribution) does not constrain negative gluon scenarios very well -> charged pions, direct photons Frank Ellinghaus, University of Colorado

  3. : enhanced sensitivity to DG and Ds? • DIS -> Ds small and negative • SIDIS HERMES (PRL 92:012005,2004) -> Ds zero or small and positive for x>0.03 • Latest HERMES result (arXiv:0803.2993) -> Ds zero or small and positive for x>0.03 • DSSV uses latest FFs from DSS, both fits include the HERMES SIDIS Data • -> node at about 0.02 • DNS also included (HERMES) SIDIS, but has less flexible func. form and • uses (quite different) FFs from KKP and Kretzer Size of Ds important for total quark spin contribution DS Frank Ellinghaus, University of Colorado

  4. PHENIX Detector Frank Ellinghaus, University of Colorado

  5. The PHENIX Detector for Spin Physics Central Detector: • g/p0/h detection • Electromagnetic Calorimeter: PbSc + PbGl, h < |0.35|, f = 2 x 90 • p+/p- • Drift Chamber • Ring Imaging Cherenkov Detector Muon Arms: • J/y • Muon ID/Muon Tracker (m+m-) • p0 • Electromagnetic Calorimeter (MPC) Global Detectors: • Relative Luminosity • Beam-Beam Counter (BBC) • Zero-Degree Calorimeter (ZDC) • Local Polarimetry -ZDC Frank Ellinghaus, University of Colorado

  6. PHENIX longitudinally polarized pp Runs Frank Ellinghaus, University of Colorado

  7. h reconstruction via gg decay • Energy asymmetry cut: E1-E2 / E1+E2 < 0.7 • pT > 2 GeV • |zvertex| < 30 cm • Fit:Gauss+Pol3 2<pT<3 GeV Frank Ellinghaus, University of Colorado

  8. Invariant cross section L = integrated Luminosity, based on Vernier scan using the BBC BR= Branching ratio: h 2 photons = 0.3943 ± 0.0026 fAcc = acceptance function from MC (includes smearing) effTrig (Minimum Bias data) = Trigger efficiency of MB trigger effTrig (high pT triggered data) = (Trigger effi. MB) x (Trigger effi. high pT trigger) effrec = Correct for h loss due to photon conversion (~6% in PBSC, ~8% in PbGl) x loss due to cut on shower shape (~4%) N = number of reconstructed h Frank Ellinghaus, University of Colorado

  9. facc from Monte Carlo Acceptance and smearing correction from MC (also accounts for dead regions in EmCal, minimum cuts on photon energies,…) data MC Up to 10% acceptance in PbSc for h at high pT pT Frank Ellinghaus, University of Colorado

  10. Photon/MB Trigger Efficiency Minimum Bias (MB) trigger efficiency about 80 % Photon trigger efficiency roughly stable from 4 GeV on (high pT photon trigger threshold is set to 1.4 GeV) Frank Ellinghaus, University of Colorado

  11. h cross section • Run 6 h cross section analysis in progress, goes up to 20 GeV! • No h fragmentation functions (FFs) in the literature! • Enables extraction of FFs from e+e- data and this (large range in pT) pp • result ( gluon FFs). • Extraction uses method/code from DSS (de Florian, Sassot, Stratmann, • PRD75, 2007) -> Frank Ellinghaus, University of Colorado

  12. h FFs - Data Frank Ellinghaus, University of Colorado

  13. h FFs - Comparison Describes e+e- data very well over a large range in energies. preliminary Will include low-energy high-precision (prelim.) BABAR data and PHENIX RUN 6 cross section (25 data points out to 20 GeV) soon. Hope for HERMES SIDIS data…… Frank Ellinghaus, University of Colorado

  14. PHENIX Run-05 Preliminary 200 GeV h Cross section @ 200 GeV NLO pQCD calculation (m = pT) by M. Stratmann (uses this h FF, so more a self-consistency check) • subprocess fraction needed for extraction of DG Frank Ellinghaus, University of Colorado

  15. h / p0 • has (slightly) enhanced sensitivity to gg (when compared to p0) as expected • Enhanced gg contribution leads to • larger asymmetries than for p0 • sizeable differences in the asymmetry • only for max/min scenarios • With DG small in currently measured • region the difference between p0 • and h asymmetries is small compared • to the current stat. error. Frank Ellinghaus, University of Colorado

  16. Access to Ds? Up to 10% contribution from strange quarks…. (Caution: Potentially large uncertainty on s-quark FF due to absence of SIDIS data!) Frank Ellinghaus, University of Colorado

  17. 2 < pT < 3 GeV/c 3 < pT < 4 GeV/c 4 < pT < 5 GeV/c 5 < pT < 6 GeV/c Mgg (MeV) Mgg (MeV) Mgg (MeV) Mgg (MeV) Inclusive h Asymmetries in pp -> h X Relative luminosity R using beam-beam counters Frank Ellinghaus, University of Colorado

  18. Measure Access to DG: Add the pieces… Access to polarized gluon distribution function via double helicity asymmetry in inclusive polarized pp scattering: subprocess asym+frac (FFs) from DIS Max and min scenarios excluded by h. Frank Ellinghaus, University of Colorado

  19. Cross section - pQCD applicability RUN5 200 GeV -- p0 • p0: pQCD seems at work, with still • sizeable scale uncertainties for • pT<5 GeV • Charged pion cross section so far only • extracted from MB triggered data set; • PID with TOF • ->low pT only • Also charge separated cross sections • extracted by PHENIX • “high” pT triggered (EmCal+RICH) data set; • charged pions begin firing the RICH at • pT~4.7 GeV, • cross section extraction in progress … PRD76:051106,2007 Frank Ellinghaus, University of Colorado

  20. Fraction of pion production p+, p –, p0 and the sign of DG Especially in the region where qg scattering is dominant (pT > 5 GeV), the increasing contribution of d quarks (Dd<0) leads to: “Model independent” conclusion possible once enough data is available. Frank Ellinghaus, University of Colorado

  21. Comparison to model calculations • Charge separated FFs (DSS, PRD75, 2007) available using SIDIS data (HERMES • preliminary); Calculations by W. Vogelsang • New Run 6 (2006) result in agreement with Run 5 (2005) • More data needed-> Projection for Run 9 (2009) w/o maybe additional higher pT point Frank Ellinghaus, University of Colorado

  22. q g q Direct Photons at s=200 GeV Dominated by qg Compton: -> small unc. from FFs -> better access to sign of DG (Dq times DG) Run-5 Theoretically clean “Golden Channel” is luminosity hungry… Frank Ellinghaus, University of Colorado

  23. Summary • Charged pion and h data are getting ready to be included in (the next round of) global QCD fits, thanks to new/improved FFs….some more data needed too. Frank Ellinghaus, University of Colorado

More Related