Recent PHENIX results on     and  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

Frank Ellinghaus, University of Colorado Spin Sum Rule: The latest… DSSV, arXiv: First “global” (DIS+SIDIS+pp) analysis! HERMES, arXiv: Gluons carry half the momentum. Do they carry half the spin?  G small in measured range. Gluon orbital momentum? Contribution at small or large x? PHENIX  0 (large gg contribution) does not constrain negative gluon scenarios very well -> charged pions, direct photons

Frank Ellinghaus, University of Colorado : enhanced sensitivity to  G and  s? DIS ->  s small and negative SIDIS HERMES (PRL 92:012005,2004) ->  s zero or small and positive for x>0.03 Latest HERMES result (arXiv: ) ->  s 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  s important for total quark spin contribution 

Frank Ellinghaus, University of Colorado PHENIX Detector

Frank Ellinghaus, University of Colorado The PHENIX Detector for Spin Physics Central Detector:    detection –Electromagnetic Calorimeter: PbSc + PbGl,  < |0.35|,  = 2 x 90      –Drift Chamber –Ring Imaging Cherenkov Detector Muon Arms: J  –Muon ID/Muon Tracker (  )   –Electromagnetic Calorimeter (MPC) Global Detectors: Relative Luminosity –Beam-Beam Counter (BBC) –Zero-Degree Calorimeter (ZDC) Local Polarimetry - ZDC

Frank Ellinghaus, University of Colorado PHENIX longitudinally polarized pp Runs Year  s [GeV] Recorded LPol [%]FOM (P 4 L) 2003 (Run-3) pb nb (Run-4) pb nb (Run-5) pb nb (Run-6) pb nb (Run-6) pb nb -1

Frank Ellinghaus, University of Colorado  reconstruction via  decay Energy asymmetry cut: E 1 -E 2 / E 1 +E 2 < 0.7 p T > 2 GeV |z vertex | < 30 cm Fit: Gauss+Pol3 2<p T <3 GeV

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

Frank Ellinghaus, University of Colorado f acc from Monte Carlo Acceptance and smearing correction from MC (also accounts for dead regions in EmCal, minimum cuts on photon energies,…) Up to 10% acceptance in PbSc for  at high p T data MC pTpT

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

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

Frank Ellinghaus, University of Colorado  FFs - Data ExperimentSystemEnergy (GeV)# Points ALEPH ’92e+e ALEPH ’00e+e ALEPH ‘02e+e L3 ‘92e+e L3 ’94e+e OPALe+e ARGUSe+e-106 CELLOe+e-354 HRSe+e-2913 JADE ’85e+e JADE ‘’90e+e MARK IIe+e-297 PHENIX 2  p+p20012 PHENIX 3  p+p2006 PHENIX ’05 prelim.p+p20019

Frank Ellinghaus, University of Colorado  FFs - Comparison Describes e+e- data very well over a large range in energies. 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…… preliminary

Frank Ellinghaus, University of Colorado  Cross 200 GeV PHENIX Run-05 Preliminary 200 GeV NLO pQCD calculation (  = p T ) by M. Stratmann (uses this  FF, so more a self-consistency check)  subprocess fraction needed for extraction of  G

Frank Ellinghaus, University of Colorado  /  0  has (slightly) enhanced sensitivity to gg (when compared to  0 ) as expected Enhanced gg contribution leads to larger asymmetries than for  0 sizeable differences in the asymmetry only for max/min scenarios With  G small in currently measured region the difference between   and  asymmetries is small compared to the current stat. error.

Frank Ellinghaus, University of Colorado Access to  s? 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 Inclusive  Asymmetries in pp  X Relative luminosity R using beam-beam counters 2 < p T < 3 GeV/c M  (MeV) 3 < p T < 4 GeV/c4 < p T < 5 GeV/c5 < p T < 6 GeV/c M  (MeV)

Frank Ellinghaus, University of Colorado Access to  G: Add the pieces… Access to polarized gluon distribution function via double helicity asymmetry in inclusive polarized pp scattering: Measure from DISsubprocess asym+frac (FFs) Max and min scenarios excluded by 

Frank Ellinghaus, University of Colorado Cross section - pQCD applicability RUN5 200 GeV --  0 Charged pion cross section so far only extracted from MB triggered data set; PID with TOF ->low p T only Also charge separated cross sections extracted by PHENIX “high” p T triggered (EmCal+RICH) data set; charged pions begin firing the RICH at p T ~4.7 GeV, cross section extraction in progress … PRD76:051106,2007  0 : pQCD seems at work, with still sizeable scale uncertainties for p T <5 GeV

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

Frank Ellinghaus, University of Colorado 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 p T point

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

Frank Ellinghaus, University of Colorado Summary Charged pion and  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.