1,187 research outputs found
Nonextensive hydrodynamics for relativistic heavy-ion collisions
The nonextensive one-dimensional version of a hydrodynamical model for
multiparticle production processes is proposed and discussed. It is based on
nonextensive statistics assumed in the form proposed by Tsallis and
characterized by a nonextensivity parameter . In this formulation the
parameter characterizes some specific form of local equilibrium which is
characteristic for the nonextensive thermodynamics and which replaces the usual
local thermal equilibrium assumption of the usual hydrodynamical models. We
argue that there is correspondence between the perfect nonextensive
hydrodynamics and the usual dissipative hydrodynamics. It leads to simple
expression for dissipative entropy current and allows for predictions for the
ratio of bulk and shear viscosities to entropy density, and ,
to be made.Comment: Final version accepted for publication in Phys. Rev.
Coulomb corrections to inclusive cross sections at the future Electron - Ion Collider
The experimental results of the future electron -- ion () collider are
expected to constrain the dynamics of the strong interactions at small values
of the Bjorken -- variable and large nuclei. Recently it has been suggested
that Coulomb corrections can be important in inclusive and diffractive
interactions. In this paper we present a detailed investigation of the impact
of the Coulomb corrections to some of the observables that will be measured in
the future collider. In particular, we estimate the magnitude of these
corrections for the charm and longitudinal cross sections in inclusive and
diffractive interactions. Our results demonstrate that the Coulomb corrections
for these observables are negligible, which implies that they can be used to
probe the QCD dynamics.Comment: 9 pages, 6 figures. Improved version to be published in Physical
Review
Heavy quark & direct photon production and heavy quark parton densities
Direct photon production in association with a heavy quark can serve as an
excellent tool for the study of the heavy quark distributions. Currently it is
believed that heavy quarks are produced radiatively inside the nucleon, and so
there is no need to take into account heavy quark parameters inside global PDF
analyses. Certain models taking into account the possibility of an intrinsic
charm component exist. Here we present how these affect the \gamma + c cross
section. While at pA collisions the potential of this process to constrain the
gluon nuclear PDF which is currently largely unconstrained is presented.Comment: Quarkonium 2010 Proceeding
Progress in the determination of the cross section
Improving previous calculations, we compute the cross section using QCD sum rules. Our sum rules for the , , and hadronic
matrix elements are constructed by using vaccum-pion correlation functions, and
we work up to twist-4 in the soft-pion limit. Our results suggest that, using
meson exchange models is perfectly acceptable, provided that they include form
factors and that they respect chiral symmetry. After doing a thermal average we
get mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file
Methodologies in Identification, Analysis, and Measurement of Visual Pollution: The Case Study of Intramuros
The problem of visual pollution in the Philippines has been increasingly evident, and people are becoming aware of it. But to create effective solutions, a deep understanding of the problem should first be established. This paper was aimed to identify, analyze, and measure the visual pollution present in Intramuros, a heritage city in the Philippines that encapsulates the Philippine colonial architecture in the 1890s. The site is known for its preservation of its city image but also modern landscape changes. To achieve the goal, the application of the Indirect and Direct Method of Landscape Evaluation was executed. These methods led to two results: (1) the identification of components— which are landscape attributes and indicators, that make up a visual landscape; and (2) the understanding of how it is perceived by the observer through a survey and interviews, which are quantified by ratings. To further understand the relationship of indicators and ratings with each other, a series of correlational studies was done. This resulted to the establishment of Disturbance, Stewardship, and Image Rating as the primary descriptors of visual pollution. A weighted average formula was then established, which quantified the visual pollution of Intramuros through indicator values and response ratings. It was concluded that visual pollution in Intramuros, through research-based methodology, can be identified, analyzed, and measured. Specific viewpoints in the district were identified as unacceptably visually-polluted. Magallanes St. cor. Victoria St. in Intramuros had the highest VP Score at -4.886. Elements that contributed to visual pollution were also identified
J/Psi Propagation in Hadronic Matter
We study J/ propagation in hot hadronic matter using a four-flavor
chiral Lagrangian to model the dynamics and using QCD sum rules to model the
finite size effects manifested in vertex interactions through form factors.
Charmonium breakup due to scattering with light mesons is the primary
impediment to continued propagation. Breakup rates introduce nontrivial
temperature and momentum dependence into the J/ spectral function.Comment: 6 Pages LaTeX, 3 postscript figures. Proceedings for Strangeness in
Quark Matter 2003, Atlantic Beach, NC, March 12-17, 2003; minor corrections
in version 2, to appear in J. Phys.
Charmonium Cross Sections and the QGP
In this short review we summarize experimental information and theoretical
results for the low-energy dissociation cross sections of charmonia by light
hadrons. These cross sections are required for the simulation of charmonium
absorption through collisions with comovers in heavy ion collisions, which
competes with quark-gluon plasma production as a charmonium-suppression
mechanism. If the cross sections are sufficiently large these dissociation
reactions may be misinterpreted as an effect of quark-gluon plasma production.
Theoretical predictions for these RHIC-related processes have used various
methods, including a color-dipole scattering model, meson exchange models,
constituent interchange models and QCD sum rules. As the results have been
largely unconstrained by experiment, some of the predictions differ by orders
of magnitude, notably in the near-threshold regime that is most relevant to QGP
searches.Comment: 7 pages, 11 figures. Expanded and updated version of a presentation
to QNP-2002 (Juelich, 9-14 June 2002
Looking for intrinsic charm in the forward region at BNL RHIC and CERN LHC
The complete understanding of the basic constituents of hadrons and the
hadronic dynamics at high energies are two of the main challenges for the
theory of strong interactions. In particular, the existence of intrinsic heavy
quark components in the hadron wave function must be confirmed (or disproved).
In this paper we propose a new mechanism for the production of -mesons at
forward rapidities based on the Color Glass Condensate (CGC) formalism and
demonstrate that the resulting transverse momentum spectra are strongly
dependent on the behavior of the charm distribution at large Bjorken . Our
results show clearly that the hypothesis of intrinsic charm can be tested in
and collisions at RHIC and LHC.Comment: 22 pages, 5 figures. Version to be published in Nuclear Physics
Dissociation cross sections of ground-state and excited charmonia with light mesons in the quark model
We present numerical results for the dissociation cross sections of
ground-state, orbitally- and radially-excited charmonia in collisions with
light mesons. Our results are derived using the nonrelativistic quark model, so
all parameters are determined by fits to the experimental meson spectrum.
Examples of dissociation into both exclusive and inclusive final states are
considered. The dissociation cross sections of several C=(+) charmonia may be
of considerable importance for the study of heavy ion collisions, since these
states are expected to be produced more copiously than the J/psi. The relative
importance of the productions of ground-state and orbitally-excited charmed
mesons in a pion-charmonium collision is demonstrated through the -dependent charmonium dissociation cross sections.Comment: 9 pages, 8 figure
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