J/ nuclear modification factor in nucleus-nucleus collisions

Xiao-Ming Xu

outline

• a brief review of J/ mechanisms in medium

• J/ nuclear modification factor in nucleus-nucleus collisions

• summary

• J/ and the critical point

fundamental processes stimulated by SPS

dissociation in QGP

T. Matsui, H. Satz, Phys. Lett. B178 (1986) 416

color screening

M.E. Peskin, Nucl. Phys. B156 (1979) 365

G. Bhanot, M.E. Peskin, Nucl. Phys. B156 (1979) 391

D. Kharzeev, H. Satz, Phys. Lett. B334 (1994) 155

ccJg /

dissociation in hadronic matter(1) constant cross sections

J/ + hadron charmed mesons (charmed baryons)

Dissociation cross sections of J/ in collisions with hadrons are assumed to be independent of the center-of-mass energy of J/ and hadron.

J. Ftacnik et al., Phys. Lett. B207 (1988) 194S. Gavin et al., Phys. Lett. B207 (1988) 257R. Vogt et al., Phys. Lett. B207 (1988) 263C. Gerschel et al., Phys. Lett. B207 (1988) 253

dissociation in hadronic matter(2) quark model calculations

J/ + hadron charmed mesons (charmed baryons)

Barnes-Swanson quark-interchange modelThe dissociation cross sections depend on the center-

of-mass energy of J/ and hadron.

K. Martins et al., Phys. Rev. C51 (1995) 2723C.-Y. Wong et al., Phys. Rev. C65 (2001) 014903T. Barnes et al., Phys. Rev. C68 (2003) 014903X.-M. Xu et al., Nucl. Phys. A713 (2003) 470

Prior form: gluon propagation before quark interchange

Post form: gluon propagation after quark interchange

dissociation in hadronic matter(3) meson exchange model calculations

J/ + hadron charmed mesons (charmed baryons)

hadronic effective Lagrangians

The dissociation cross sections depend on the center-of-mass energy of J/ and hadron.

S.G. Matinyan, B. Muller, Phys. Rev. C58 (1998) 2994

K .Haglin, Phys. Rev. C61 (2000) 031902

Z. Lin, C.M. Ko, Phys. Rev. C62 (2000) 034903

············

fundamental processes stimulated by RHIC

recombination mechanism

X.-M. Xu, Nucl. Phys. A658 (1999) 165P. Braun-Munzinger, J. Stachel, Phys. Lett. B490 (2000) 196 R.L. Thews, M. Schroedter, J. Rafelski, Phys. Rev. C63 (200

1) 054905

x/ Jcc

Spectral function analysis in quenched QCD

dissociation temperature of > 1.5Tc

dissociation temperature of ~ 1.1Tc

M. Asakawa, T. Hatsuda, Phys. Rev. Lett. 92 (2004) 012001

/J

c

Challenge: Can we discover a new mechanism for J/

at LHC?

Model predictions on J/ produced in nucleus-nucleus collisions

X.-M. Xu, Nucl. Phys. A697 (2002) 825

history of high-energy nucleus-nucleus collisions

AA QGM (no T) QGP HM

1 2 3 5

history of high-energy nucleus-nucleus collisions

1. initial nucleon-nucleon collisions;

2. thermalization of quark-gluon matter;

3. evolution of quark-gluon plasma;

4. hadronization at a critical temperature;

5. evolution of hadronic matter until freeze-out.

production of cc

is a pointlike color singlet or a color octet pair from

is produced in the initial nuclear collisions, during the thermalization of quark-gluon matter, in the evolution of quark-gluon plasma.

cc

cc

x:22 ccba

ccba :12

recombination

In quark-gluon matter probability for to form a bound state J/ (cJ, ´) is proportional to the product of the NRQCD nonperturbative matrix elements and a medium modification factor.

cc

cc

NRQCD nonperturbative matrix elements

Ο8H(3S1) = constant, Ο8

H(1S0) = constant,

Ο8H(3P0) = constant

Ο8H(3S1)=χ+σTa ψ · (a+

HaH)ψ+σTaχ

Ο8H(1S0)=χ+Ta ψ (a+

HaH) ψ+Taχ

ψ the field that annihilates a heavy quark.

χ the field that creates a heavy antiquark.

χ)2

(ψ)aa(ψ)2

(χ3

1)( HH0

3H8

aa TDi

TDi

PO ��

medium modification factors

S-wave color-octet state

P-wave color-octet state

medium: quark-gluon matter (no T and T)

cross section

)(v'exp T][rel )8(

min

0

tVdndScgcg

)(v'exp T][rel )8(

min

0

tVdndPcgcg

ccLnccg JS ][ )8(12:

][ )8(Lcgc

dissociation

penetrates through deconfined matter and hadronic matter, interacts with partons in deconfined matter

interacts with hadrons in hadronic matter

,][ )1(12 ccLnccg JS

qccqLnccqq JS ][ )1(12

cc

two definitions

• Charmonium is prompt if the point at which the charmonium state is produced and the collision point of the colliding beams cannot be resolved using a vertex detector.

A charmonium coming from the decay of b-hadrons is not prompt.

• Charmonium is direct if the charmonium is prompt but does not come from the decay of a higher charmonium state.

The prompt J/ includes direct J/ as well as the radiative feeddown from direct cJ and direct .

= short-distance production recombination dissociation

charmonium from initial nuclear collisions

charmonium from prethermal stage

charmonium from thermal stage

pdyd

dN2

)1( /2

22

Aaini S

pdyd

dN

pdyd

dN pre

2

22

pdyd

dN pre

2

12

pdyd

dNthe2

12

pdyd

dNthe2

22

pT- and y- spectra

Momentum distribution of J/:

produced via recombination during the thermalization of quark-gluon matter and in the evolution of quark-gluon plasma cause enhancement of J/ in some momentum region.

ratio:

The ratio is the J/ nuclear modification factor.

pdyd

dN

pdyd

dN

pdyd

dN

pdyd

dNS

pdyd

dN

pdyd

dN thetheprepreAa

ini2

22

2

12

2

22

2

12

/2

22

2)1(

cc

NNAA

AA pdydAdN

pdyddN

R

22

left: pT distribution J/ right: rapidity distribution

ratio versus pT at y=0, central Au-Au collisions, 200GeV

ratio versus rapidity at pT=4 GeV/c, central Au-Au collisions, 200GeV

nuclear modification factors for high-pT J/ in Cu-Cu collisions --- from Hugo Pereira Da Costa’s talk

PHENIX Minimum Bias STAR + PHENIX Central collisions

nuclear modification factors for high-pT J/ in Au-Au collisions --- from Duncan Prindle’ talk

Au+Au: 0-80%Star preliminary

SUMMARY

(1) Mechanisms: dissociation and recombination.

(2) Has the study of J/ at both SPS and RHIC accomplished the discovery of mechanisms for J/ in nucleus-nucleus collisions?

(3) Competition between charmonium dissociation and charmonium formed from charm quarks and antiquarks in deconfined matter.

(4) J/ enhancement in some momentum region

Suggest J/ as a probe of the critical point

Reason:

On one side of the critical point, confined matter,

no recombination of charm quark and charm antiquark.

On the other side of the critical point, deconfined matter,

recombination of charm quark and charm antiquark.

The nuclear modification factor of J/ is affected by the recombination.

Method:

1. system size dependence of RAA

2. beam energy dependence of RAA

Find a critical point in Fig. 5 of Phys. Rev. Lett. 98, 232301 (2007)

Azimuthal Asymmetry of J/ Production

X.-N. Wang, F. Yuan, Phys. Lett. B540 (2002) 62

J/ is affected only by

v2 ( pT=3 GeV, NP=130 ) 0.022 at RHIC

Z.W. Lin, D. Molnar, Phys. Rev. C68 (2003) 044901

V. Greco, C.M. Ko, R. Rapp, Phys. Lett. B595 (2004) 202

L. Yan, P. Zhuang, N. Xu, Phys. Rev. Lett. 97 (2006) 232301

J/ is affected by dissociation

and recombination

ccJg /

ccJg /gJcc /