3,234 research outputs found
Quasinormal modes and dispersion relations for quarkonium in a plasma
Recent investigations show that the thermal spectral function of heavy and vector mesons can be described using holography.
These studies consider a bottom up model that captures the heavy flavour
spectroscopy of masses and decay constants in the vacuum and is consistently
extended to finite temperature. The corresponding spectral functions provide a
picture of the dissociation process in terms of the decrease of the quasi-state
peaks with temperature.
Another related tool that provides important information about the thermal
behaviour is the analysis of the quasinormal modes. They are field solutions in
a curved background assumed to represent, in gauge/gravity duality,
quasi-particle states in a thermal medium. The associated complex frequencies
are related to the thermal mass and width. We present here the calculation of
quasinormal modes for charmonium and bottomonium using the holographic
approach. The temperature dependence of mass and thermal width are
investigated. Solutions corresponding to heavy mesons moving into the plasma
are also studied. They provide the dependence of the real and imaginary parts
of the frequency with the quasi-particle momenta, the so called dispersion
relations.Comment: V2: enlarged version with clarifications, more comparison with
previous articles and additional references included. 11 figures, 2 tables,
62 references. Version accepted for publication in JHE
Bottomonium dissociation in a finite density plasma
We present a holographic description of the thermal behavior of
heavy vector mesons inside a plasma at finite temperature and density. The
meson dissociation in the medium is represented by the decrease in the height
of the spectral function peaks. In order to find a description for the
evolution of the quasi-states with temperature and chemical potential it is
crucial to use a model that is consistent with the decay constant behavior. The
reason is that the height of a spectral function peak is related to the value
of the zero temperature decay constant of the corresponding particle. AdS/QCD
holographic models are in general not consistent with the observation that
decay constants of heavy vector mesons decrease with radial excitation level.
However, it was recently shown that using a soft wall background and
calculating the correlation functions at a finite position of anti-de Sitter
space, associated with an ultraviolet energy scale, it is possible to describe
the observed behavior. Here we extend this proposal to the case of finite
temperature and chemical potential . A clear picture of the
dissociation of bottomonium states as a function of and emerges
from the spectral function. The energy scales where the change in chemical
potential leads to changes in the thermal properties of the mesons is
consistent with QCD expectations.Comment: In V3: errors in reference citations corrected. Version published in
Physics Letters B. 15 pages, 3 figure
Configuration entropy and stability of bottomonium radial excitations in a plasma with magnetic fields
Heavy vector mesons produced in a heavy ion collision are important sources
of information about the quark gluon plasma (QGP). For instance, the fraction
of bottomonium states observed in such a collision is altered by the
dissociation effect caused by the plasma. So, it is very important to
understand how the properties of the plasma, like temperature , density
and the presence of background magnetic fields , affect the dissociation
of bottomonium in the thermal medium. AdS/QCD holographic models provide a tool
for investigating the properties of heavy mesons inside a thermal medium. The
meson states are represented by quasinormal modes in a black hole geometry. In
this work we calculate the quasinormal modes and the associated complex
frequencies for the four lowest levels of radial excitation of bottomonium
inside a plasma with a magnetic field background. We also calculate the
differential configuration entropy (DCE) for all these states and investigate
how the dissociation effect produced by the magnetic field is translated into a
dependence of the DCE on . An interesting result obtained in this study is
that the DCE increases with the radial excitation level . Also, a nontrivial
finding of this work is that the energy density associated with the bottomonium
quasinormal modes presents a singularity near the black hole horizon for some
combination of values of and . As we show here, it is possible to
separate the singular factor and define a square integrable quantity that
provides a DCE that is always finite. In addition, we discovered that, working
with the potentially singular energy density, one finds a very interesting way
to use the DCE as a tool for determining the dissociation temperature of the
meson quasisates.Comment: 22 pages, 2 tables and 10 figures with 26 subfigures in total. In
version 2, we show an original result concerning the use of the differential
configuration entropy to characterize the dissociation temperature of the
physical system studied. Some clarifications were also include
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