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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 /