1. W. Xie (Riken-BNL Research Center) for PHENIX Collaboration
Study of J/y Production in √snn=200GeV p-p and d-Au Collisions at PHENIX
W. Xie (Riken-BNL Research Center) for
PHENIX Collaboration
Content:
Physics Motivation
How PHENIX measure J/ψ
PHENIX results on J/ψ production in run3 p-p and d-Au collisions
Summary
08/07/2005
QM2005, Budapest, Hungary

2. 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:
rapidity y
Gluon (anti-)shadowing X1 X2
J/ in
South
y < 0
Nuclear absorption. X1 X2
J/ in
North
y > 0
Initial state energy loss.
Cronin effect
gluons in Pb / gluons in p
South (y < -1.2) :
large X2 (in gold) ~ 0.090
Central (y ~ 0) :
intermediate X ~ 0.020
North (y > 1.2) :
small X2 (in gold) ~ 0.003
Anti
Shadowing
Shadowing X
Eskola, et al., Nucl. Phys. A696 (2001)

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, (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/
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)

6. J/y rapidity Distribution in p-p and d-Au Collisions
R. Vogt: EKS98 shadowing. 3mb absorption
p-p J/Psi – PHENIX 200GeV
Rapidity
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) )
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/ )

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

11. 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
Rapidity
One of the major uncertainty comes from limited statistics in run3 p-p collisions.

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

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