04/20/23 QM2005, Budapest, Hungary 1

Study of J/ 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

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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:

• Cronin effect

• Gluon (anti-)shadowing

• Nuclear absorption.

• Initial state energy loss.

gluons in Pb / gluons in p

X

Shadowing

Eskola, et al., Nucl. Phys. A696 (2001) 729-746.

AntiShadowing

X1 X2

J/ inNorthy > 0

X1X2

J/ inSouthy < 0

rapidity y

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

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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

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Good momentum resolution and muon identification from ID and Trk.

High rate capability: powerful level-1 dimuon trigger

How PHENIX Measure J/ψ

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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

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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

R. Vogt: EKS98 shadowing. 3mb absorption

J/ rapidity Distribution in p-p and d-Au Collisions

Note: The cross section is misrepresented as 2.16 µb during the QM05 presentation

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pT broadening: Cronin Effect

Parton initial state multiple scattering leads to broadening of J/ pT distribution

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Broadening in forward J/ψ production comparable to lower energy (s = 39 GeV in E866)

x2~ 0.01

x2~ 0.003

x2~ 0.1

pT broadening: Cronin Effect

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 ?

)1972( ppdA

<pT2>= 3.03±0.40

( misrepresented as 3.17±0.33 atQM05 )

<pT2>= 4.31±0.85

(misrepresented as 4.20±0.76 at QM05)

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Nuclear Dependence on xbj and xF: Initial State Energy Loss

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)

)1972( ppdA

xbj

•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)

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Rapidity and Ncoll Dependence of RdAu: Gluon Shadowing and Nuclear Absorption

• Data favor weak shadowing and weak nuclear absorption effect.

• More suppression for more central events.

RdA

0

0.2

0.4

0.6

0.8

1.0

1.2

Rapidity

)1972/( ppdAdAR ppinvcoll

dAinv

dA YieldN

YieldR

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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.

Rapidity

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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

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•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.

Summary

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Backup slides

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