共查询到20条相似文献,搜索用时 15 毫秒
1.
N. Jachowicz G. C. McLaughlin 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):43-47
We argue that isotropization and, consequently, thermalization of the system of gluons and quarks produced in an ultrarelativistic
heavy-ion collision does not follow from Feynman diagram analysis to any order in the coupling constant. We conclude that
the apparent thermalization of quarks and gluons, leading to success of perfect fluid hydrodynamics in describing heavy-ion
collisions at RHIC, can only be attributed to the non-perturbative QCD effects not captured by Feynman diagrams. We proceed
by modeling these non-pertrubative thermalization effects using viscous hydrodynamics. We point out that matching Color Glass
Condensate inital conditions with viscous hydrodynamics leads to a continuous evolution of all the components of the energy-momentum
tensor and, unlike the case of ideal hydrodynamics, does not give rise to a discontinuity in the longitudinal pressure. An
important consequence of such a matching is a relationship between the thermalization time and shear viscosity: we observe
that small viscosity leads to short thermalization time. 相似文献
2.
Selected results from the first five years of RHIC data taking are reviewed with emphasis on the evidence for thermalization
in central Au + Au collisions at
= 200GeV. 相似文献
3.
L. Cunqueiro E. G. Ferreiro C. Pajares 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):845-847
The fluctuations due to the clustering of color sources can explain the behaviour of the scaled multiplicity variance and
transverse momentum fluctuations with centrality. They also predict a nonmonotonic behaviour with centrality for the multiplicity
associated to high-pT events. The clustering of color sources gives rise to an increase in the long-range correlations with centrality as well
as to a supression at high centrality with respect to superposition models. 相似文献
4.
We study the evolution of heavy quarkonium states with temperature in a Quark-Gluon Plasma (QGP) by evaluating an in-medium
Qˉ T-matrix within a reduced Bethe-Salpeter equation in S- and P-wave channels. The interaction kernel is extracted from finite-temperature QCD lattice calculations of the singlet free energy
of a Qˉ pair. Quarkonium bound states are found to gradually move across the Qˉ threshold after which they rapidly dissolve in the hot system. We calculate Euclidean-time correlation functions and compare
to results from lattice QCD. We also study finite-width effects in the heavy-quark propagators. 相似文献
5.
M. Schwamb 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):39-42
Three-gluon to three-gluon scatterings lead to rapid thermalization of gluon matter created in central Au-Au collisions at
RHIC energies. Thermalization of quark matter is studied from three-quark to three-quark scatterings. 相似文献
6.
D. Kharzeev 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):83-87
Inelastic hadron interactions at high energies are accompanied by a pulse of a strong chromo-electric field. This field leads
to the decay of QCD vacuum which proceeds through the emission of partons with a thermal spectrum. In a semi-classical treatment,
the effective temperature of the spectrum is determined by the acceleration of partons in the classical chromo-electric field,
in accord with the general arguments given by Hawking and Unruh. 相似文献
7.
We present here a brief summary of the presentation given at the Quark-Gluon-Plasma Thermalization Workshop in Vienna, Austria in August 2005, directly following the International Quark Matter Conference in Hungary. 相似文献
8.
We study the baryon-quark phase transition in the molecular dynamics (MD) of the quark degrees of freedom at finite baryon
density. The baryon state at low baryon density, and the deconfined quark state at high baryon density are reproduced. We
investigate the equations of state of matters with different u-d-s compositions. It is found that the baryon-quark transition is sensitive to the quark width. 相似文献
9.
M. J. Leitch 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):868-874
At the Relativistic Heavy-Ion Collider (RHIC) collisions of heavy ions at nucleon-nucleon energies of 200GeV appear to have
created a new form of matter thought to be a deconfined state of the partons that ordinarily are bound in nucleons. We discuss
the evidence that a thermalized partonic medium, usually called a Quark Gluon Plasma (QGP), has been produced. Then, we discuss
the effect of this high-density medium on the production of jets and their pair correlations. Next, we look at direct photons
as a clean electro-magnetic probe to constrain the initial hard scatterings. Finally, we review the developing picture for
the effect of this medium on the production of open heavy quarks and on the screening by the QGP of heavy-quark bound states. 相似文献
10.
R. L. Thews 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):15-18
We examine the possibility to utilize in-medium charmonium formation in heavy-ion interactions at collider energy as a probe
of the properties of the medium. This is possible because the formation process involves recombination of charm quarks which
imprints a signal on the resulting normalized transverse momentum distribution containing information about the momentum distribution
of the quarks. We have contrasted the transverse momentum spectra of J/ψ, characterized by 〈p
T
2〉, which result from the formation process in which the charm quark distributions are taken at opposite limits with regard
to thermalization in the medium. The first uses charm quark distributions unchanged from their initial production in a pQCD
process, appropriate if their interaction with the medium is negligible. The second uses charm quark distributions which are
in complete thermal equilibrium with the transversely expanding medium, appropriate if a very strong interaction between charm
quarks and medium exists. We find that the resulting 〈p
T
2〉 of the formed J/ψ should allow one to differentiate between these extremes, and that this differentiation is not sensitive to variations
in the detailed dynamics of in-medium formation. We include a comparison of predictions of this model with preliminary PHENIX
measurements, which indicates compatibility with a substantial fraction of in-medium formation. 相似文献
11.
We show that large fluctuations of D-mesons kinetic-energy (or momentum) distributions might be a signature of a phase transition to the Quark-Gluon Plasma (QGP).
In particular, a jump in the variance of the momenta or kinetic energy, as a function of a control parameter (temperature
or Fermi energy at finite baryon densities) might be a signature for a first-order phase transition to the QGP. This behavior
is completely consistent with the order parameter defined for a system of interacting quarks both at zero temperature (and
finite baryon densities) or at finite temperatures which shows a jump in correspondence with a first-order phase transition
to the QGP. The J/Ψ displays exactly the same behavior of the order parameter and of the variance of the D-mesons. We discuss implications for relativistic heavy-ion collisions within the framework of a transport model and possible
hints for experimental search. 相似文献
12.
W.M. Alberico P. Czerski M. Nardi 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):195-203
We present a three–dimensional model for quark matter with a density dependent quark–quark (confining) potential, which allows
to describe a sort of deconfinement transition as the system evolves from a low density assembly of bound structures to a
high density free Fermi gas of quarks. We consider different confining potentials, some of which successfully utilized in
hadron spectroscopy. We find that a proper treatment of the many–body correlations induced by the medium is essential to disentangle
the different nature of the two (hadronic and deconfined) phases of the system. For this purpose the ground state energy per
particle and the pair correlation function are investigated.
Received: 10 June 1998 / Revised version: 24 September 1998 相似文献
13.
T. Hirano 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):19-22
We can establish a new picture, the perfect fluid sQGP core and the dissipative hadronic corona, of the space-time evolution
of produced matter in relativistic heavy-ion collisions at RHIC. It is also shown that the picture works well also in the
forward rapidity region through an analysis based on a new class of the hydro-kinetic model and that this is a manifestation
of the rapid increase of the entropy density in the vicinity of QCD critical temperature, namely, deconfinement. 相似文献
14.
G. Chanfray D. Davesne J. Delorme M. Ericson J. Marteau 《The European Physical Journal A - Hadrons and Nuclei》2000,8(2):283-289
This paper is devoted to the evaluation of the pionic scalar density at finite temperature and baryonic density. We express
the latter effect in terms of the nuclear response evaluated in the random phase approximation. We discuss the density and
temperature evolution of the pionic density which governs the quark condensate evolution. Numerical evaluations are performed.
Received: 7 December 1999 / Accepted: 8 May 2000 相似文献
15.
D. d'Enterria 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):816-823
We present a summary of the physics of gluon saturation and non-linear QCD evolution at small values of the parton momentum
fraction x in the proton and nucleus in the context of recent experimental results at HERA and RHIC. The rich physics potential of low-x studies at the LHC, especially in the forward region, is discussed and some benchmark measurements in pp, pA and AA collisions are introduced. 相似文献
16.
W. M. Alberico S. Chiacchiera H. Hansen A. Molinari M. Nardi 《The European Physical Journal A - Hadrons and Nuclei》2008,38(1):97-103
We consider the shear viscosity of a system of quarks and its ratio to the entropy density above the critical temperature
for deconfinement. Expressions for both quantities are derived in the quasi-particle approximation and calculations are carried
out for different modeling of the quark self-energy, also allowing for a temperature dependence of the effective mass and
width. Beyond the temperature dependence, the behaviour of the viscosity and the entropy density is discussed in terms of
the strength of the coupling and of the main characteristics of the quark self-energy. A comparison with existing approaches
is also discussed. 相似文献
17.
T. Matsuki T. Morii K. Sudoh 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):701-704
The recent discovery of Ds states suggests the existence of radial excitations. Our semirelativistic quark potential model succeeds in reproducing these
states within one to two percent of accuracy compared with the experiments, D
s0(2860) and D
s
*(2715), which are identified as 0+ and 1- radial excitations (n = 2). We also present calculations of radial excitations for B/B
s heavy mesons. The relation between our formulation and the modified Goldberger-Treiman relation is also described. 相似文献
18.
Based on our work hep-ph/0510121, we discuss further the numerical study of classical SU(2) 3+1-D Yang-Mills equations for matter produced in a high-energy heavy-ion collision. The growth of the amplitude of fluctuations
as exp(Γ
) (where g
2μ is a scale arising from the saturation of gluons in the nuclear wave function) is shown to be robust over a wide range of
initial amplitudes that violate boost invariance. We argue that this growth is due to a non-Abelian Weibel instability, the
scale of which is set by a dynamically generated plasmon mass. We discuss the relation of Γ to the prediction from kinetic
theory. 相似文献
19.
I. Bombaci 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):810-815
We examine the present status of the theoretical calculations for the internal structure of neutron stars, and the connection
with the microscopic properties of ultradense hadronic matter. We discuss the possibility to have quark deconfinement phase
transition in the core of neutron stars, and we explore some of its astrophysical implications as the quark-deconfinement
nova model for gamma-ray bursts. 相似文献
20.
T. Schäfer 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):403-408
We review many-body calculations of the equation of state of dilute neutron matter in the context of effective-field theories
of the nucleon-nucleon interaction. 相似文献