4,529 research outputs found
Azimuthal Asymmetry of Direct Photons in High Energy Nuclear Collisions
We show that a sizeable azimuthal asymmetry, characterized by a coefficient
v_2, is to be expected for direct photons produced in non-central high energy
nuclear collisions. This signal is generated by photons radiated by jets
interacting with the surrounding hot plasma. The anisotropy is out of phase by
an angle with respect to that associated with the elliptic anisotropy
of hadrons, leading to negative values of v_2. Such an asymmetry, if observed,
could be a signature for the presence of a quark gluon plasma and would
establish the importance of jet-plasma interactions as a source of
electromagnetic radiation.Comment: New title. Final versio
Information sharing and credit : firm-level evidence from transition countries
We investigate whether information sharing among banks has affected credit market performance in the transition countries of Eastern Europe and the former Soviet Union, using a large sample of firm-level data. Our estimates show that information sharing is associated with improved availability and lower cost of credit to firms. This correlation is stronger for opaque firms than transparent ones and stronger in countries with weak legal environments than in those with strong legal environments. In cross-sectional estimates, we control for variation in country-level aggregate variables that may affect credit, by examining the differential impact of information sharing across firm types. In panel estimates, we also control for the presence of unobserved heterogeneity at the firm level, as well as for changes in macroeconomic variables and the legal environment
Chemical composition of the decaying glasma
The the initial stage of a relativistic heavy ion collision can be described
by a classical color field configuration known as the Glasma. The production of
quark pairs from this background field is then computed nonperturbatively by
numerically solving the Dirac equation in the classical background. The result
seems to point towards an early chemical equilibration of the plasma.Comment: 8 pages, 5 figures, invited talk at Stangeness in Quark Matter 2006
(SQM06), UCLA, March 200
The QCD confinement transition: hadron formation
We review the foundations and the applications of the statistical and the
quark recombination model as hadronization models.Comment: 45 pages, 16 figures, accepted for publication in Landolt-Boernstein
Volume 1-23
High Energy Nuclear Collisions: Theory Overview
We review some basic concepts of Relativistic Heavy Ion Physics and discuss
our understanding of some key results from the experimental program at the
Relativistic Heavy Ion Collider (RHIC). We focus in particular on the early
time dynamics of nuclear collisions, some result from lattice QCD, hard probes
and photons.Comment: 11 pages, 3 figures; delivered at ISNP 2009, published in Praman
Statistical Physics and Light-Front Quantization
Light-front quantization has important advantages for describing relativistic
statistical systems, particularly systems for which boost invariance is
essential, such as the fireball created in a heavy ion collisions. In this
paper we develop light-front field theory at finite temperature and density
with special attention to quantum chromodynamics. We construct the most general
form of the statistical operator allowed by the Poincare algebra and show that
there are no zero-mode related problems when describing phase transitions. We
then demonstrate a direct connection between densities in light-front thermal
field theory and the parton distributions measured in hard scattering
experiments. Our approach thus generalizes the concept of a parton distribution
to finite temperature. In light-front quantization, the gauge-invariant Green's
functions of a quark in a medium can be defined in terms of just 2-component
spinors and have a much simpler spinor structure than the equal-time fermion
propagator. From the Green's function, we introduce the new concept of a
light-front density matrix, whose matrix elements are related to forward and to
off-diagonal parton distributions. Furthermore, we explain how thermodynamic
quantities can be calculated in discretized light-cone quantization, which is
applicable at high chemical potential and is not plagued by the
fermion-doubling problem.Comment: 30 pages, 3 figures; v2: Refs. added, minor changes, accepted for
publication in PR
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