9,555 research outputs found
Dilepton and photon production in the presence of a nontrivial Polyakov loop
We calculate the production of dileptons and photons in the presence of a
nontrivial Polyakov loop in QCD. This is applicable to the semi-Quark Gluon
Plasma (QGP), at temperatures above but near the critical temperature for
deconfinement. The Polyakov loop is small in the semi-QGP, and near unity in
the perturbative QGP. Working to leading order in the coupling constant of QCD,
we find that there is a mild enhancement, ~ 20%, for dilepton production in the
semi-QGP over that in the perturbative QGP. In contrast, we find that photon
production is strongly suppressed in the semi-QGP, by about an order of
magnitude, relative to the perturbative QGP. In the perturbative QGP photon
production contains contributions from 2->2 scattering and collinear emission
with the Landau- Pomeranchuk-Migdal (LPM) effect. In the semi-QGP we show that
the two contributions are modified differently. The rate for 2->2 scattering is
suppressed by a factor which depends upon the Polyakov loop. In contrast, in an
SU(N) gauge theory the collinear rate is suppressed by 1/N, so that the LPM
effect vanishes at infinite N. To leading order in the semi-QGP at large N, we
compute the rate from 2->2 scattering to the leading logarithmic order and the
collinear rate to leading order
Degrees of Freedom of the Quark Gluon Plasma, tested by Heavy Mesons
Heavy quarks (charm and bottoms) are one of the few probes which are
sensitive to the degrees of freedom of a Quark Gluon Plasma (QGP), which cannot
be revealed by lattice gauge calculations in equilibrium. Due to the rapid
expansion of the QGP energetic heavy quarks do not come to an equilibrium with
the QGP. Their energy loss during the propagation through the QGP medium
depends strongly on the modelling of the interaction of the heavy quarks with
the QGP quarks and gluons, i.e. on the assuption of the degrees of freedom of
the plasma. Here we compare the results of different models, the pQCD based
Monte-Carlo (MC@sHQ), the Dynamical Quasi Particle Model (DQPM) and the
effective mass approach, for the drag force in a thermalized QGP and discuss
the sensitivity of heavy quark energy loss on the properties of the QGP as well
as on non-equilibrium dynamicsComment: proceedings symposion "New Horizons" Makutsi, South Africa, Nov 201
Kappa-deformed Statistics and the Formation of a Quark-Gluon Plasma
The effect of the non-extensive form of statistical mechanics proposed by
Tsallis on the formation of a quark-gluon plasma (QGP) has been recently
investigated in ref. \cite{1}. The results show that for small deviations
() from Boltzmann-Gibbs (BG) statistics in the QGP phase, the
critical temperature for the formation of a QGP does not change substantially
for a large variation of the chemical potential. In the present effort we use
the extensive -deformed statistical mechanics constructed by Kaniadakis
to represent the constituents of the QGP and compare the results with ref. [1].Comment: 2 Figure
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