512 research outputs found
A large- PNJL model with explicit Z symmetry
A PNJL model is built, in which the Polyakov-loop potential is explicitly
Z-symmetric in order to mimic a Yang-Mills theory with gauge group
SU(). The physically expected large- and large- behaviours of the
thermodynamic observables computed from the Polyakov-loop potential are used to
constrain its free parameters. The effective potential is eventually
U(1)-symmetric when is infinite. Light quark flavours are added by using
a Nambu-Jona-Lasinio (NJL) model coupled to the Polyakov loop (the PNJL model),
and the different phases of the resulting PNJL model are discussed in 't
Hooft's large- limit. Three phases are found, in agreement with previous
large- studies. When the temperature is larger than some deconfinement
temperature , the system is in a deconfined, chirally symmetric, phase for
any quark chemical potential . When however, the system is in a
confined phase in which chiral symmetry is either broken or not. The critical
line , signalling the restoration of chiral symmetry, has the same
qualitative features than what can be obtained within a standard PNJL
model.Comment: To appear in Phys Rev
QCD effective action with a most general homogeneous field background
We consider one-loop effective action of SU(3) QCD with a most general
constant chromomagnetic (chromoelectric) background which has two independent
Abelian field components. The effective potential with a pure magnetic
background has a local minimum only when two Abelian components H_{\mu\nu}^3
and H_{\mu\nu}^8 of color magnetic field are orthogonal to each other. The
non-trivial structure of the effective action has important implication in
estimating quark-gluon production rate and p_T-distribution in quark-gluon
plasma. In general the production rate depends on three independent Casimir
invariants, in particular, it depends on the relative orientation between
chromoelectric fields.Comment: 6 pages, 3 figures (9 pages in published version
Does parton saturation at high density explain hadron multiplicities at RHIC ?
We discuss the recent claim that hadron multiplicities measured at RHIC
energies are directly described in terms of gluon degrees of freedom fixed from
the initial conditions of central heavy ion collisions. The argument is based
on the parton saturation scenario expected to be valid at high parton densities
and on the assumption of conserved gluon number. Alternatively we conjecture
that "bottom-up" equilibration before hadronization modifies this picture, due
to nonconservation of the number of gluons.Comment: 8 page
Bottom-up thermalization in heavy ion collisions
We describe how thermalization occurs in heavy ion collisions in the
framework of perturbative QCD. When the saturation scale is large
compared to , thermalization takes place during a time of order
and the maximal temperature achieved is
.Comment: 11 pages; acknowledgement added; section IIIB slightly extended,
version accepted for publication in Phys. Lett.
Open and hidden charm production in heavy ion collisions at ultrarelativistic energies
We consider the production of the open charm and J/psi mesons in heavy ion collisions at BNL RHIC. We discuss several recently developed pictures for J/psi production and argue that a measurement at RHIC energies is crucial for disentangling these di erent descriptions
What are we learning from RHIC?
This talk is an attempt to summarize some of the first results obtained at
RHIC. I discuss the significance of these measurements for establishing the
properties of hot and dense QCD matter and for understanding the dynamics of
the theory at the high parton density, strong color field frontier.Comment: 11 pages, 6 figures, invited talk given at the XX International
Symposium on Lattice Field Theory ``Lattice 2002'', Cambridge, MA, June 24 -
29, 200
Heavy flavour production in DGLAP improved saturation model
The charm and beauty quark production in deep inelastic scattering at low
values of the Bjorken variable x is considered in the DGLAP improved saturation
model. After fitting parameters of the model to the structure function F_2, the
heavy quark contributions Fc_2 and Fb_2 are predicted. A good description of
the data is found. Predictions for the longitudinal structure function F_L and
the diffractive structure function FD_2 are also presented.Comment: 16 pages, 7 figures; typos corrected, references added, final
Phys.Rev. D versio
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