p+p J/  results from PHENIX Run-2 Hiroki Sato, Kyoto University for the PHENIX collaboration RBRC Workshop “ Current and Future Directions at RHIC ” BNL, Upton, NY Aug. 15, 2002

Heavy-flavor measurements with RHIC/PHENIX Open and bound-state heavy flavors are identified with PHENIX using their (semi-) leptonic decays J/  and   e + e -,  +  - Open charm and open bottom  Single e(  ), ee, , e  bb  e  X direct  cc  eX RHIC:  s=200GeV

J/  production in p+p collisions at  s = 200 GeV The highest energy measurement of the total cross section Discriminate theoretical models for the production mechanism Reference point for Au+Au data  s dependence of the J/  total cross section with previous lower-energy experiments

Theoretical models for the J/  production Color-Evaporation Model (CEM)  “Ignore” color and other quantum numbers of a cc pair  Certain fraction (free parameter) of all produced cc pairs form each charmonium Color-Single Model (CSM)  Non-Relativistic (small v c ) QCD  Only a cc pair with the color-singlet state and the same quantum numbers can form each charmonium  No free parameter  Cross section disagrees with Tevatron data Color-Octet Model (COM)  Different state of a cc pair (including color-octet states) can form a charmonium with (a) soft gluon emission(s).  Color-octet matrix elements are extracted from data  still in controversial  Polarization of the high-p T J/  disagrees with Tevatron data

The PHENIX Detector in Run-2 Central Arms to detect hadrons, electrons and photons  |  | < 0.35  p T > 0.2GeV/c South Muon Arm to detect muons in the forward region  1.2 <  < 2.2  p tot > 2GeV/c Beam-Beam Counter (BBC) to trigger p+p interactions  3.0 < |  | < 3.9  Trigger efficiency ~ 50% for p+p inelastic events Independent measurements of J/  using both e + e - channel and  +  - channel

RHIC Integrated p ＋ p Luminosity RHIC delivered 700nb -1 to PHENIX After online vertex cuts, PHENIX recorded 150 nb -1 Present preliminary analysis used data from: 81 nb -1 (1.7 x 10 9 )  +  - 48 nb -1 (1.0 x 10 9 ) e + e nb -1 Days PHENIX 1/1/02

The PHENIX Muon Arm Detect muons with p tot >2GeV/c, 1.2<  <2.2 (South Arm) Pre-hadron-rejection with Central Magnet steel ( int ~5) Muon Tracking Chamber (MuTr)  Measure momentum of muons with cathode-readout strip chambers at 3 stations inside Muon Magnet Muon Identifier (MuID)   /µ separation with 5-layer sandwich of chambers (Iarocci tubes) and steel  Trigger muons Successfully operated first time during Run-2 MuID MuTr Muon Magnet

Muon LVL-1 Trigger  Coincidence of fired MuID planes of each “quadrant”  One quadrant for “single-muon trigger” and more than one quadrant for “dimuon trigger”  used for this analysis  Inefficiencies from hardware dead time is 1~2% ‘Quadrant’ trigger µ MuID Quadrant

J/    +  - signal Significant enhancement of unlike-sign pair in the J/  mass region Peak (3156  74 MeV/c 2 ) is consistent with J/  mass Mass width (257  75 MeV/c 2 ) is consistent with expectation  further improvement is expected 36 counts in 2.5<mass<3.7GeV/c assuming same count of unlike and like-sign pairs from background (confirmed with simulation) Systematic error on the count ~10 % by changing mass cut GeV

Normalizations for the muon channel N J/  : Number of measured J/  in 1.2<y<2.2 A cc : South Muon Arm Acceptance ×reconstruction efficiency for J/  (1.2<y<2.2)  µ + µ - with the ideal detector  MuID : Real MuID trigger and road efficiency  MuTr : Real MuTr track efficiency  BBC J/  : BBC efficiency for J/  events L: Luminosity with good vertex cut (|z-vertex|<38cm)  y: rapidity coverage = 1.0

MuID trigger and road efficiencies Realistic panel-by-panel efficiencies are used in simulation (obtained from minimum bias real data) Single muon trigger×road efficiency ~ 0.80 Dimuon trigger×road efficiency ~ 0.62 Systematic uncertainty (run dependence) ~ 11% Ratio (road efficiency)/(trigger ×road efficiency) is consistent with real data (~0.9) Panel efficiency (%) Number of panels

MuTr Track efficiency MuTr inefficiency is caused mainly due to dead HV and dead FEM during the run Efficiency for dimuons ~ 0.23 MuTr efficiency obtained using MuID roads is consistent with simulation except Octant-5 and Octant-7 10% systematic error is assigned from this inconsistency Run dependence is <4% Better efficiency is expected in the next Run Azimuthal angle of roads (degree) MuTr efficiency  (number of roads with a track) / (number of roads) MuTr efficiency

J/  Acceptance × reconstruction efficiency with real chamber efficiencies J/  rapidity J/  p T (GeV/c) 1.2<y<2.2 = p T dependence is small Uncertainty from the unknown J/  polarization is assigned to be 10% A cc  MuID  MuTr

BBC efficiency and luminosity  inela : p+p inelastic cross section (PYTHIA,  s fit)  BBC J/  : BBC efficiency for p+p  J/  +X  µ + µ - events p T (J/  ) dependence is small consistent with p+p  J/  +X  e + e - (0.75) and p+p   0 X (0.75)  BBC inela : BBC efficiency for p+p inelastic events N int : Number of interaction triggers with vertex cut (|z|<38cm) simulation Real data Analysis of  BBC inela  inela is still in progress Assign conservative 20% error on it

Br d  /dy| y=1.7 result and its uncertainties Center valueUncertainty N J/psi 36 (2.5<mass<3.7GeV/c 2 )19% (statistical) 10% (cut dependence) A cc  MuID  MuTr (1.2<y<2.2) 10% (J/  pol. dep., |  |<0.3) 11% (MuID efficiency) 10% (MuTr efficiency)  BBC J/  L 60nb -1 20% (consistency with machine value) <5% (Trigger counter efficiency) Br(J/  +  - ) d  J/  /dy| y=1.7. = 37  7(stat.)  11(syst.) nb PHENIX Preliminary

J/  p T distribution 1.2<y<2.2 p T distribution (shape) is consistent with PYTHIA (color-singlet model) prediction

Electron Measurement with the Central Arms Charged tracks are identified with Drift Chambers (DC) and Pad Chambers (PC1/2/3) Ring Imaging CHerenkov detector (RICH) and Electro-Magnetic Calorimeter (EMCal, i.e. PbSc/PbGl) are used to identify electrons EMCal is also used for electron/photon Trigger

Electron LVL-1 Trigger and its Efficiency EMCal 2x2 towers non- overlapping sum (threshold=0.8GeV)  single electron/photon trigger Trigger efficiency for J/  is expected to  Use Monte-Carlo tuned to describe single-photon efficiencies with real data well e +- 1 PMT (Tower) 2x2 EMCal 11cm

J/  e + e - Signal N J/  = 24  6 (stat.)  4 (syst.)

J/  e + e - Acceptance and Reconstruction Efficiency  acc  eff =  Flat rapidity distribution in |y|<0.5 is assumed Uncertainties from unknown p T distribution is estimated to be 7%

Br d  /dy| y = 0 result. N J/  = 24  6(stat.)  4(syst.)  acc  eff =   run-run = 0.87  0.09  additional Run-by-Run correction factor  trig = – 0.07  BBC J/  = 0.75  0.11 L = 48  10 nb -1  y = 1.0  Br(J/  e + e - ) d  /dy| y = 0 =52  13 (stat.)  18 (syst.) nb PHENIX Preliminary

J/  Rapidity distribution and Total cross section Rapidity distribution is consistent with PYTHIA A global fit gives µ+µ-µ+µ- e+e-e+e- Br(J/  l + l - )  (total) = 226  36 (stat.)  79 (syst.) nb  (total) = 3.8  0.6 (stat.)  1.3 (syst.) µb PHENIX Preliminary

Total Cross section compared with the Color-Evaporation Model prediction CEM Parameters are fixed by fitting low energy data Our result agrees with the CEM prediction at  s=200GeV Fixed target experiments Phys. Lett. B390,323(1997)

Color-Singlet Model prediction  (J/  ) in  b Direct J/  0.28  c2 decay 0.31  c1 decay 0.06 Total0.65 Other contributions will be small (  ’, b-quark) Disagrees with our result by factor ~6 PYTHIA p+p  s=200GeV GRV94LO Gluon fusion only

Color-Octet Model prediction Work in progress Large uncertainties from extraction of color- octet matrix elements, charm-quark mass, PDF, and so on. Needs theorists’ help to predict  Total cross section  Polarization  p T distribution

In Run-3 and later Much higher statistics (>10 times) leads to  Measurement of the J/  polarization (spin alignment)  critical test to separate CEM and COM  More precise measurement of the p T slope Longitudinally polarized proton-proton collisions  Double-longitudinal spin asymmetry (A LL ) of the J/  production  polarized gluon density

Summary Cross section of inclusive J/  production was measured with PHENIX using both e + e - decay channel (|y|<0.35) and  +  - decay channel (1.2<y<2.2) in Run-2 p+p collisions at  s = 200GeV Br(J/  +  - ) d  J/  /dy| y=1.7 = 37  7(stat.)  11(syst.) nb Br(J/  e + e - ) d  J/  /dy| y=0 = 52  13(stat.)  18(syst.) nb Rapidity fit including both results gives  J/  (total) = 3.8  0.6(stat.)  1.3(syst.) µb The result agrees with the Color-Evaporation model prediction and disagrees with the Color-Singlet Model prediction In Run-3, measurement of the J/  polarization and A LL is expected

J/  polarization dependence of acceptance There is J/  polarization dependence of acceptance because of intrinsic momentum cut (~2GeV/c) of the Muon Arm But there is no indication from previous experiment (both Fixed target energy and Tevatron) | | is larger than 0.3. Assign 10% systematic error assuming | | < 0.3. cos  *(Gottfried-Jackson frame) cos  * dependence of J/  acceptance (with real chamber efficiencies) =0 Due to momentum cut (P~2GeV/c) Quick Monte-Carlo (J/  polarization) dependence of J/  acceptance A cc  MuID  MuTr A cc