242 research outputs found
Heavy-quarks in the QGP: study of medium effects through euclidean propagators and spectral functions
The heavy-quark spectral function in a hot plasma is reconstructed from the
corresponding euclidean propagator. The latter is evaluated through a
path-integral simulation. A weak-coupling calculation is also performed,
allowing to interpret the qualitative behavior of the spectral function in
terms of quite general physical processes.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
Real and imaginary-time quarkonium correlators in a hot plasma
The possibility of describing the behavior of a pair in a hot
plasma in terms of an effective potential is investigated. It is shown that as
long as medium effects can be embodied in a gaussian action, like in the QED
case, the propagator obeys a closed temporal evolution equation
whose large-time behavior is governed by an effective potential. The latter,
beside screening, displays also an imaginary part related to collisions.Comment: Talk given at the 8-th Conference "Quark Confinement and the Hadron
Spectrum", Mainz, Germany, 1-6 September 200
A path integral for heavy-quarks in a hot plasma
We propose a model for the propagation of a heavy-quark in a hot plasma, to
be viewed as a first step towards a full description of the dynamics of heavy
quark systems in a quark-gluon plasma, including bound state formation. The
heavy quark is treated as a non relativistic particle interacting with a
fluctuating field, whose correlator is determined by a hard thermal loop
approximation. This approximation, which concerns only the medium in which the
heavy quark propagates, is the only one that is made, and it can be improved.
The dynamics of the heavy quark is given exactly by a quantum mechanical path
integral that is calculated in this paper in the Euclidean space-time using
numerical Monte Carlo techniques. The spectral function of the heavy quark in
the medium is then reconstructed using a Maximum Entropy Method. The path
integral is also evaluated exactly in the case where the mass of the heavy
quark is infinite; one then recovers known results concerning the complex
optical potential that controls the long time behavior of the heavy quark. The
heavy quark correlator and its spectral function is also calculated
semi-analytically at the one-loop order, which allows for a detailed
description of the coupling between the heavy quark and the plasma collective
modes
Heavy-flavor hadronization mechanism from pp to AA collisions: a theoretical perspective
The interest in studying heavy-flavor hadronization in high-energy nuclear
collisions is twofold. On one hand hadronization represents a source of
systematic uncertainties in phenomenological attempts of extracting
heavy-flavor transport coefficients in the Quark Gluon Plasma which one assumes
to be produced in the collision. Hence, developing the most possible reliable
model for this process is important to get a precise and accurate estimate of a
fundamental property of hot QCD. On the other hand studying how hadronization
changes in the presence of a dense medium of colored partons can be considered
an issue of interest by itself. In particular, the observation of modifications
of heavy-flavor hadronization in proton-proton collisions strongly suggests
that also in this case a small droplet of Quark-Gluon Plasma can be formed.
Here we try to provide a general overview on heavy-flavor hadronization, from
pp to AA collisions, stressing the aspects and challenges common to all
mechanisms proposed in the literature. Then, focusing on a particular model, we
show how a consistent description of several observables involving heavy-flavor
hadrons can be obtainedComment: Proceedings of the Hard Probes 2023 conferenc
Medium-induced color flow softens hadronization
Medium-induced parton energy loss, resulting from gluon exchanges between the
QCD matter and partonic projectiles, is expected to underly the strong
suppression of jets and high- hadron spectra observed in
ultra-relativistic heavy ion collisions. Here, we present the first
color-differential calculation of parton energy loss. We find that color
exchange between medium and projectile enhances the invariant mass of energetic
color singlet clusters in the parton shower by a parametrically large factor
proportional to the square root of the projectile energy. This effect is seen
in more than half of the most energetic color-singlet fragments of
medium-modified parton branchings. Applying a standard cluster hadronization
model, we find that it leads to a characteristic additional softening of
hadronic spectra. A fair description of the nuclear modification factor
measured at the LHC may then be obtained for relatively low momentum transfers
from the medium
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