770 research outputs found
Angular Dependence of the Radiative Gluon Spectrum and the Energy Loss of Hard Jets in QCD Media
The induced momentum spectrum of soft gluons radiated from a high energy
quark propagating through a QCD medium is derived in the BDMPS formalism. A
calorimetric measurement for the medium dependent energy lost by a jet with
opening angle is proposed.The fraction of this energy
loss with respect to the integrated one appears to be the relevant
observable.It exhibits a universal behaviour in terms of the variable
where is the size of the medium and
the transport coefficient. Phenomenological implications for the
differences between cold and hot QCD matter are discussed.Comment: 13 pages and 7 figures, RevTe
Parton Energy Loss with Detailed Balance
Stimulated gluon emission and thermal absorption in addition to induced
radiation are considered for an energetic parton propagating inside a quark-
gluon plasma. In the presence of thermal gluons, stimulated emission reduces
while absorption increases the parton's energy. The net effect is a reduction
of the parton energy loss. Though decreasing asymptotically as with the
parton energy, the relative reduction is found to be important for intermediate
energies. The modified energy dependence of the energy loss will affect the
shape of suppression of moderately high hadrons due to jet quenching in
high-energy heavy-ion collisions.Comment: 4 pages in RevTex with 1 postscript figure. Some typos are corrected
and new comments are adde
Where is the jet quenching in Pb+Pb collisions at 158 AGeV?
Because of the rapidly falling particle spectrum at large from jet
fragmentation at the CERN SPS energy, the high- hadron distribution should
be highly sensitive to parton energy loss inside a dense medium as predicted by
recent perturbative QCD (pQCD) studies. A careful analysis of recent data from
CERN SPS experiments via pQCD calculation shows little evidence of energy loss.
This implies that either the life-time of the dense partonic matter is very
short or one has to re-think about the problem of parton energy loss in dense
matter. The hadronic matter does not seem to cause jet quenching in
collisions at the CERN SPS. High- two particle correlation in the
azimuthal angle is proposed to further clarify this issue.Comment: 4 pages with 2 ps figures. Minors changes are made in the text with
updated references. Revised version to appear in Phys. Rev. Letter
Exact solutions to the four Goldstone modes around a dark soliton of the nonlinear Schroedinger equation
This article is concerned with the linearisation around a dark soliton
solution of the nonlinear Schr\"odinger equation. Crucially, we present
analytic expressions for the four linearly-independent zero eigenvalue
solutions (also known as Goldstone modes) to the linearised problem. These
solutions are then used to construct a Greens matrix which gives the
first-order spatial response due to some perturbation. Finally we apply this
Greens matrix to find the correction to the dark-soliton wavefunction of a
Bose-Einstein condensate in the presence of fluctuations.Comment: 14 pages, 3 figures, submitted to Journal of Physics
One-Dimensional Integrable Spinor BECs Mapped to Matrix Nonlinear Schr\"odinger Equation and Solution of Bogoliubov Equation in These Systems
In this short note, we construct mappings from one-dimensional integrable
spinor BECs to matrix nonlinear Schr\"odinger equation, and solve the
Bogoliubov equation of these systems. A map of spin- BEC is constructed from
the -dimensional spinor representation of irreducible tensor operators of
. Solutions of Bogoliubov equation are obtained with the aid of the
theory of squared Jost functions.Comment: 2.1 pages, JPSJ shortnote style. Published version. Note and
reference adde
Systematic Study of High p_T Hadron Spectra in pp, pA and AA Collisions from SPS to RHIC Energies
High- particle spectra in (), and
collisions are calculated within a QCD parton model in which intrinsic
transverse momentum, its broadening due to initial multiple parton scattering,
and jet quenching due to parton energy loss inside a dense medium are included
phenomenologically. The intrinsic and its broadening in and
collisions due to initial multiple parton scattering are found to be very
important at low energies ( GeV). Comparisons with ,
and data with different centrality cuts show that the differential
cross sections of large transverse momentum pion production ( GeV/)
in collisions scale very well with the number of binary nucleon-nucleon
collisions (modulo effects of multiple initial scattering). This indicates that
semi-hard parton scattering is the dominant particle production mechanism
underlying the hadron spectra at moderate GeV/.
However, there is no evidence of jet quenching or parton energy loss. Within
the parton model, one can exclude an effective parton energy loss
GeV/fm and a mean free path fm from the
experimental data of collisions at the SPS energies. Predictions for high
particle spectra in and collisions with and without jet
quenching at the RHIC energy are also given. Uncertainties due to initial
multiple scattering and nuclear shadowing of parton distributions are also
discussed.Comment: 13 pages in RevTex with 14 figures, the final published version (with
some typos corrected
On the Caudrey-Beals-Coifman System and the Gauge Group Action
The generalized Zakharov-Shabat systems with complex-valued Cartan elements
and the systems studied by Caudrey, Beals and Coifman (CBC systems) and their
gauge equivalent are studies. This includes: the properties of fundamental
analytical solutions (FAS) for the gauge-equivalent to CBC systems and the
minimal set of scattering data; the description of the class of nonlinear
evolutionary equations solvable by the inverse scattering method and the
recursion operator, related to such systems; the hierarchies of Hamiltonian
structures.Comment: 12 pages, no figures, contribution to the NEEDS 2007 proceedings
(Submitted to J. Nonlin. Math. Phys.
Generalized r-matrix structure and algebro-geometric solution for integrable systems
The purpose of this paper is to construct a generalized r-matrix structure of
finite dimensional systems and an approach to obtain the algebro-geometric
solutions of integrable nonlinear evolution equations (NLEEs). Our starting
point is a generalized Lax matrix instead of usual Lax pair. The generalized
r-matrix structure and Hamiltonian functions are presented on the basis of
fundamental Poisson bracket. It can be clearly seen that various nonlinear
constrained (c-) and restricted (r-) systems, such as the c-AKNS, c-MKdV,
c-Toda, r-Toda, c-Levi, etc, are derived from the reduction of this structure.
All these nonlinear systems have {\it r}-matrices, and are completely
integrable in Liouville's sense. Furthermore, our generalized structure is
developed to become an approach to obtain the algebro-geometric solutions of
integrable NLEEs. Finally, the two typical examples are considered to
illustrate this approach: the infinite or periodic Toda lattice equation and
the AKNS equation with the condition of decay at infinity or periodic boundary.Comment: 41 pages, 0 figure
High Azimuthal Asymmetry in Non-central A+A at RHIC
The high GeV azimuthal asymmetry, , in
non-central nuclear collisions at RHIC is shown to be a sensitive measure of
the initial parton density distribution of the produced quark-gluon plasma. A
generalization of the Gyulassy-Levai-Vitev (GLV) non-abelian energy loss
formalism including Bjorken 1+1D expansion as well as important kinematic
constraints is used.Comment: 4 pages, Revtex, bbox.sty, 4 eps figures, references added, minor
corrections, Phys.Rev.Lett versio
Coupled KdV equations derived from atmospherical dynamics
Some types of coupled Korteweg de-Vries (KdV) equations are derived from an
atmospheric dynamical system. In the derivation procedure, an unreasonable
-average trick (which is usually adopted in literature) is removed. The
derived models are classified via Painlev\'e test. Three types of
-function solutions and multiple soliton solutions of the models are
explicitly given by means of the exact solutions of the usual KdV equation. It
is also interesting that for a non-Painlev\'e integrable coupled KdV system
there may be multiple soliton solutions.Comment: 19 pages, 2 figure
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