共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
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
3.
J. M. Friedrich 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):620-625
Results for the spin structure of the nucleon from the COMPASS data taking periods 2002 to 2004 are presented. The quark contribution
to the nucleon spin, following from a QCD fit to the new data, turns out to be significantly larger than it was derived from
the previous world data. The new data favour, on the other side, a comparatively small gluon polarisation in the range x
g ≈ 0.1. In the data taken with the deuteron target polarised transversely the related asymmetries are found to be small on
the level of accuracy reached so far, indicating a cancellation of the proton and neutron contributions. This is in agreement,
for both the Collins and the Sivers asymmetry, with recent theoretical calculations. Also, a step towards the understanding
of angular-momentum contributions with COMPASS is taken by the evaluation of asymmetries in exclusive vector meson production. 相似文献
4.
K. Tsushima K. Saito A. W. Thomas A. Valcarce 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):626-629
We study the bound-nucleon sigma term and the quark condensate in nuclear matter. In the quark-meson coupling (QMC) model
the nuclear correction to the sigma term is small and negative, i.e., it decelerates the decrease of the quark condensate in nuclear matter. However, the quark condensate in nuclear matter is
controlled primarily by the scalar-isoscalar σ field. Compared to the leading term, it moderates the decrease more than that of the nuclear sigma term alone at densities
around and larger than the normal nuclear-matter density. 相似文献
5.
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
6.
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
7.
We investigate the evolutions with density of the QCD scalar susceptibility and of the sigma mass in a chiral relativistic theory of nuclear matter, in the mean-field approximation. In order to reach saturation we need to introduce the scalar response of the nucleons. The consequences are a quite mild density dependence of the sigma mass and the progressive decoupling of the quark density fluctuations from the nucleonic ones at large densities. 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.
10.
D. N. Aguilera 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):828-830
We present results for the spin-1 color-spin-locking (CSL) phase using a NJL-type model in two-flavor quark matter for compact
stars applications. The CSL condensate is flavor symmetric and therefore charge and color neutrality can easily be satisfied.
We find small energy gaps ≃ 1MeV, which make the CSL matter composition and the EoS not very different from the normal quark
matter phase. We keep finite quark masses in our calculations and obtain no gapless modes that could have strong consequences
in the late cooling of neutron stars. Finally, we show that the region of the phase diagram relevant for neutron star cores,
when asymmetric flavor pairing is suppressed, could be covered by the CSL phase. 相似文献
11.
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
12.
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
13.
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
14.
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
15.
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
16.
Numerical 1D-3V solutions of the Wong-Yang-Mills equations with anisotropic particle momentum distributions are presented.
They confirm the existence of plasma instabilities for weak initial fields and of their saturation at a level where the particle
motion is affected, similar to Abelian plasmas. The isotropization of the particle momenta by strong random fields is shown
explicitly, as well as their nearly exponential distribution up to a typical hard scale, which arises from scattering off
field fluctuations. By variation of the lattice spacing we show that the effects described here are independent of the UV
field modes near the end of the Brioullin zone. 相似文献
17.
B. R. Holstein 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):505-511
The subject of hadronic parity violation is nearly fifty years old, but a good deal of uncertainty remains, despite many efforts
both theoretical and experimental. A brief summary of the field is presented and a plan is proposed for new experimental work
which, when combined with a new theoretical tack based on effective field theory, should lead to resolution of the present
difficulties. 相似文献
18.
We discuss QCD sum rule constraints based on moments of vector meson spectral distributions in the vacuum and in a nuclear
medium. Sum rules for the two lowest moments of these spectral distributions do not suffer from uncertainties related to QCD
condensates of dimension higher than four. We exemplify these relations for the case of the ω meson and discuss the issue
of in-medium mass shifts from this viewpoint.
Received: 22 December 1998 / Revised version: 13 January 1999 相似文献
19.
The kinematical corrections to the structure function of the nucleon in the nucleus due to the boundness and motion of nucleons arise from the excitation of the doorway states for one-nucleon transfer reactions in the deep inelastic scattering on nuclei. 相似文献
20.
E. N. E. van Dalen C. Fuchs C Fuchs C Fuchs 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):29-42
We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations
schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the
proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitive to this adaption
and its consequences, whereas the neutron properties remains almost unaffected in neutron-rich matter. Although at present
full Brueckner calculations are still too complex to apply to finite nuclei, these relativistic Brueckner results can be used
as a guidance to construct a density-dependent relativistic mean-field theory, which can be applied to finite nuclei. It is
found that an accurate reproduction of the Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of these
coupling functions. 相似文献