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Study of J/ψ Production in √snn=200GeV p-p and d-Au Collisions at PHENIX

This study focuses on measuring J/ψ production in p-p and d-Au collisions at a center-of-mass energy of 200GeV. The results aim to disentangle cold nuclear effects and understand the suppression or enhancement of J/ψ production in the Quark-Gluon Plasma.

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Study of J/ψ Production in √snn=200GeV p-p and d-Au Collisions at PHENIX

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  1. Study of J/y Production in √snn=200GeV p-p and d-Au Collisions at PHENIX • Content: • Physics Motivation • How PHENIX measure J/ψ • PHENIX results on J/ψ production in run3 p-p and d-Au collisions • Summary W. Xie (Riken-BNL Research Center) for PHENIX Collaboration QM2005, Budapest, Hungary

  2. rapidity y X2 X1 J/ in South y < 0 Anti Shadowing Shadowing X1 X2 J/ in North y > 0 Physics Motivation: Disentangle Cold Nuclear Effects J/ψ is expected to be either suppressed or enhanced in QGP. There’s also suppression or enhancement due to cold nuclear effect: South (y < -1.2) : • large X2 (in gold) ~ 0.090 Central (y ~ 0) : • intermediate X2 ~ 0.020 North (y > 1.2) : • small X2 (in gold) ~ 0.003 • Gluon (anti-)shadowing • Nuclear absorption. • Initial state energy loss. • Cronin effect gluons in Pb / gluons in p X Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

  3. How PHENIX Measure J/ψ • high resolution tracking and momentum measurement from Drift chamber. Good electron identification from Ring Imaging Cherenkov detector (RICH) and Electromagnetic Calorimeter (EMCal). High rate capability: powerful level-1 electron trigger

  4. How PHENIX Measure J/ψ Good momentum resolution and muon identification from mID and mTrk. High rate capability: powerful level-1 dimuon trigger

  5. What has been Measured so far for J/ψ Production • at s = 200 GeV p-p collisions in RUN2(150nb-1) and RUN3 (350nb-1) • Run2 results published at PRL 92, 051802(2004) • at s = 200 GeV d-Au collisions at RUN3 (2.74nb-1) • Preliminary results presented in QM04 and other major conferences • With p-p results, submitted to PRL, preprint nucl-ex/0507032. • Also see M. Leitch’s poster: • Production and Nuclear Effects for d + Au and p + p Collisions at √s = 200 GeV • at s = 200 GeV Au-Au collisions in RUN2 (24µb-1),Run4 (241µb-1) • see H. Pereira’s presentation on PHENIX Run4 J/Psi measurement • at s = 200 GeV Cu-Cu collisions in RUN5 (3nb-1) and s = 62 GeV Cu-Cu collisions Run5 (0.19nb-1) • see H. Pereira’s presentation on PHENIX Run4 J/Psi measurement

  6. p-p J/Psi – PHENIX 200GeV R. Vogt: EKS98 shadowing. 3mb absorption Rapidity J/y rapidity Distribution in p-p and d-Au Collisions The total cross section (see note) in p-p collisions is: 2.61+/-0.20(fit)+/-0.26(abs) µb Note: The cross section is misrepresented as 2.16 µb during the QM05 presentation

  7. pT broadening: Cronin Effect Parton initial state multiple scattering leads to broadening of J/y pT distribution

  8. pT broadening: Cronin Effect x2~ 0.1 <pT2>= 3.03±0.40 ( misrepresented as 3.17±0.33 atQM05 ) x2~ 0.01 <pT2>= 4.31±0.85 (misrepresented as 4.20±0.76 at QM05) x2~ 0.003 d-Au Central arm result is flat. <pT2> in p-p is much higher (4.31±0.85 GeV2) than muon arm (2.51±0.21 GeV2). Indicate anything new ? Broadening in forward J/ψ production comparable to lower energy (s = 39 GeV in E866)

  9. Nuclear Dependence on xbj and xF: Initial State Energy Loss • No xbj scaling expected for shadowing effect. • Parents gluon loose energy via hadronization before the hard scattering to form ccbar pairs. • Energy loss is weaker and shadowing becomes stronger with increasing s since the ccbar coherence length increase with energy (B. Kopeliovich et al., Nuclear Physics A696 (2001) 669-714) xbj The xF scaling behavior in low collision energy could be • an coincidence of convoluted effect for shadowing, energy loss and nuclear absorption ? • Sudakov effect ? (hep-ph/0501260)

  10. 1.2 1.0 0.8 RdA 0.6 0.4 0.2 0 Rapidity and Ncoll Dependence of RdAu: Gluon Shadowing and Nuclear Absorption Rapidity • Data favor weak shadowing and weak nuclear absorption effect. • More suppression for more central events.

  11. Rapidity What’s the Cold Nuclear Effect in Au-Au Collsions Nuclear suppression can be obtained directly from d-Au collisions. • Need more data to have an accurate baseline measurement • One of the major uncertainty comes from limited statistics in run3 p-p collisions.

  12. Phenix muon arm 1st Upsilons at RHIC ! poster: Production in √s = 200 GeV p + p Collisions at PHENIX in 2005 S. Butsyk, M.Leitch for PHENIX Collaboration We Have a Lot More Data from p-p Collisions in RUN5! PHENIX accumulated ~3pb-1 p-p collision during 2005 run.

  13. Summary • Comparison with low energy results shows the trend consistent with the theory prediction that shadowing and nuclear absorption are dominant at RHIC. • observed cronin effect in forward J/Psi measurements while results at midrapidity shows no cronin effect. • observed weak suppression from shadowing and absorption in small Bjorken x region. Suppression increase weakly toward more central region. • Large statistics of p-p collision data is being analyzed. • A modest baseline measurement to study J/Psi production in Au-Au collision has been obtained. • More d-Au run is needed.

  14. Backup slides

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