共查询到20条相似文献,搜索用时 0 毫秒
1.
S. Kimura A. Bonasera S. Cavallaro 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):89-93
We compute by numerical integration of the Dirac equation the number of quark-antiquark pairs produced in the classical color
fields of colliding ultrarelativistic nuclei. Results for the dependence of the number of quarks on the strength of the background
field, the quark mass and time are presented. We also perform several tests of our numerical method. While the number of qˉ pairs is parametrically suppressed in the coupling constant, we find that in this classical field model it could even be
compatible with the thermal ratio to the number of gluons. 相似文献
2.
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
3.
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
4.
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
5.
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
6.
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
7.
A. Kozlov 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):836-841
The production of the low-mass dielectrons is considered to be a powerful tool to study the properties of the hot and dense
matter created in the ultra-relativistic heavy-ion collisions. We present the preliminary results on the first measurements
of the low-mass dielectron continuum in Au + Au collisions and the φ-meson production measured in Au + Au and d + Au collisions at
= 200GeV performed by the PHENIX experiment. 相似文献
8.
St. Mrówczyński 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):875-882
Due to anisotropic momentum distribution the parton system produced at the early stage of relativistic heavy-ion collisions
is unstable with respect to the magnetic plasma modes. The instabilities isotropize the system and thus speed up the process
of its equilibration. The scenario of instabilities-driven isotropization is reviewed. 相似文献
9.
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
10.
The Geant4 CHIPS model simulates both decay and nuclear capture of negative muons. In hadron level models the muon is captured
by a proton, p(μ,νμ)n , and the neutron transfers to the nucleus only 5MeV, which is not enough to split a nucleon from the nucleus, while the
measured spectra of emitted nucleons reach 80MeV. In CHIPS, which considers asymptotically free quark-partons, the muon can
be captured by a quark, u(μ,νμ)d , and transfers 52MeV to the nucleus. This capture mechanism fits the main part of the nucleon spectra, while the high-energy
part of the spectra is not fitted. A precise fit of the high-energy part of the nucleon spectra can be made if the muon decay
μ → dˉνμ is taken into account. 相似文献
11.
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
12.
V. Chandra A. Ranjan V. Ravishankar 《The European Physical Journal A - Hadrons and Nuclei》2009,40(1):109-117
We study the response functions (chromo-electric susceptibilities) for an interacting quark-gluon plasma. The interaction
effects have been encoded in the effective fugacities for quasi-partons which are extracted self-consistently from the two
equations of state for hot QCD. The first one is the fully perturbative O(g
5) EOS and the second one, which is O(g
6ln(1/g)) , incorporates some non-perturbative effects. We find that the response function shows large deviations from the ideal
behavior. We further determine the temperature dependence of the Debye mass by fixing the effective coupling constant Q2 which appears in the transport equation. We show that our formalism naturally yields the leading-order HTL expression for
the Debye mass if we employ the ideal EOS. Employing the Debye mass, we estimate the dissociation temperatures for various
charmonium and bottomonium bound states. These results are consistent with the current theoretical studies. 相似文献
13.
J. Hüfner Y.B. He B.Z. Kopeliovich 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):239-244
Prompt gluons are an additional source for charmonium suppression in nuclear collisions, in particular for nucleus-nucleus
collisions. These gluons are radiated as bremsstrahlung in N-N collisions and interact inelastically with the charmonium states
while the nuclei still overlap. The spectra and mean number <n
g> of the prompt gluons are calculated perturbatively and the inelastic cross section σabs
Ψg is estimated. The integrated cross sections σ(A B →J/ψX) for p-A and A-B collisions and the dependence on transverse energy for S-U and Pb-Pb can be described quantitatively with
some adjustment of one parameter <n
g>σabs
Ψg.
Received: 20 August 1999 相似文献
14.
M. S. Bhagwat A. Krassnigg P. Maris C. D. Roberts 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):630-637
In this summary of the application of Dyson-Schwinger equations to the theory and phenomenology of hadrons, some deductions
following from a nonperturbative, symmetry-preserving truncation are highlighted, notable amongst which are results for pseudoscalar
mesons. We also describe inferences from the gap equation relating to the radius of convergence of a chiral expansion, applications
to heavy-light and heavy-heavy mesons, and quantitative estimates of the contribution of quark orbital angular momentum in
pseudoscalar mesons; and recapitulate upon studies of nucleon electromagnetic form factors. 相似文献
15.
M. V. Kossov 《The European Physical Journal A - Hadrons and Nuclei》2007,34(3):283-291
The Geant4 quark level CHIPS (CHiral Invariant Phase Space) model simulates nuclear reactions assuming asymptotic freedom
of massless quarks uniformly distributed over invariant phase space. Electro-nuclear reactions are simulated generating low-Q2 equivalent photons. In this paper generalisation of the model for high Q2 is made to describe neutrino-nuclear reactions, where the low-Q2 contribution is suppressed by the W -boson mass. The proposed non-perturbative approximation of structure functions fits high-energy lepto-nucleon reactions
with high-Q2 and neutrino-nucleon reactions starting from the threshold. 相似文献
16.
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
17.
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
18.
We study anomalous J/Ψ suppression and p
t broadening in the model of prompt gluons. The anomalous suppression can be successfully described in this model. The transverse-momentum
dependence of J/Ψ suppression in relativistic heavy-ion collisions is calculated from initial-state gluon rescattering with both nucleons
and prompt gluons produced in nucleon-nucleon collisions in the early phase of the reaction. It seems impossible to describe
simultaneously anomalous suppression and p
t broadening in Pb-Pb collisions within the model of prompt gluons with reasonable values of the parameters.
Received: 27 September 2001 / Accepted: 12 November 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: zhuangpf@mail.singhua.edu.cn
Communicated by A. Molinari 相似文献
19.
The growth rate for instabilities in an expanding parton plasma is investigated by using a quasiparticle transport model
including hadronization. The coupled Boltzmann equations for partons and pions with time dependent mean field masses and source
terms are solved in the Bjorken boost invariant picture. Hadronization modifies the known instability in the parton plasma
created by the mean field in two ways: In the beginning, hadronization increases the rate Γ of instability, but then Γ→ 0
when the hadronization is dominating the time evolution.
Received: 11 January 1999 相似文献
20.
Charm quark energy loss in QCD matter 总被引:1,自引:0,他引:1
The energy loss of heavy quarks in a quark-gluon plasma of finite size is studied within the light-cone path integral approach. A simple analytical formulation of the radiative energy loss of heavy quarks is derived. This provides a convenient way to quantitatively estimate the quark energy loss. Our results show that if the energy of a heavy quark is much larger than its mass, the radiative energy loss approaches the radiative energy loss of light quarks. 相似文献