3,034 research outputs found
Modeling the jet quenching, thermal resonance production and hydrodynamical flow in relativistic heavy ion collisions
The event topology in relativistic heavy ion collisions is determined by
various multi-particle production mechanisms. The simultaneous model treatment
of different collective nuclear effects at high energies (such as a hard
multi-parton fragmentation in hot QCD-matter, thermal resonance production,
hydrodynamical flows, etc.) is actual but rather complicated task. We discuss
the simulation of the above effects by means of Monte-Carlo model HYDJET++.Comment: Talk given at Workshop "Hot Quarks 2010" (La Londe Les Maures,
France, June 21-26, 2010); 4 pages including 2 figures as EPS-files; prepared
using LaTeX package for publication in Journal of Physics: Conference Serie
BRAHMS Overview
A brief review of BRAHMS measurements of bulk particle production in RHIC
Au+Au collisions at is presented, together with some
discussion of baryon number transport. Intermediate measurements in
different collision systems (Au+Au, d+Au and p+p) are also discussed in the
context of jet quenching and saturation of the gluon density in Au ions at RHIC
energies. This report also includes preliminary results for identified
particles at forward rapidities in d+Au and Au+Au collisions.Comment: 8 pages 6 figures, Invited plenary talk at 5th International
Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2005),
Salt Lake City, Kolkata, India, 8-12 Feb 200
Color Skyrmions in the Quark-Gluon Plasma
We consider the general formulation of nonabelian fluid dynamics based on
symmetry considerations. We point out that, quite generally, this admits
solitonic excitations which are the color analog of skyrmions. Some general
properties of the solitons are discussed.Comment: LaTeX, 13 pages, references adde
Overview of Hard processes at RHIC: high-pt light hadron and charm production
An overview of the experimental results on high-pt light hadron production
and open charm production is presented. Data on particle production in
elementary collisions are compared to next-to-leading order perturbative QCD
calculations. Particle production in Au+Au collisions is then compared to this
baseline.Comment: 9 pages, 6 figures, Strange Quark Matter 200
Rethinking the QCD collisional energy loss
It is shown that to leading order the collisional energy loss of an energetic
parton in the hot quark gluon plasma reads , where
the scale of the coupling is determined by the (parametrically soft) Debye
screening mass. Compared to previous expressions derived by Bjorken and other
authors, , the rectified result takes
into account the running of the coupling, as dictated by quantum corrections
beyond tree level. As one significant consequence, due to asymptotic freedom,
the QCD collisional energy loss becomes independent of the jet energy in the
limit . It is advocated that this resummation improved perturbative
result might be useful to (re-)estimate the collisional energy loss for
temperatures relevant in heavy ion phenomenology.Comment: contribution to "Hot Quarks 2006", Villasimius, Italy, 15-20 May 200
Gluon shadowing in the Glauber-Gribov model
New data from HERA experiment on (diffractive) deep inelastic scattering has
been used to parameterize nucleon and Pomeron structure functions. Within the
Gribov theory, the parameterizations were employed to calculate gluon shadowing
for various heavy ions and compared our results with predictions from other
models. Calculations for d+Au collisions at forward rapidities at
ultra-relativistic energies have been made and are compared to RHIC data on the
nuclear modification factor. Results for gluon shadowing are also confronted
with recent data on the nuclear modification factor at GeV at
various values of the Feynman variable , and the energy dependence of the
effect is discussed.Comment: To appear in the proceedings of the Workshop for young scientists on
the physics of ultrarelativistic nucleus-nucleus collisions, Hot Quarks 2006.
To be published in EPJ
Jet quenching in relativistic heavy ion collisions
Parton propagation in dense nuclear matter results in elastic, inelastic and
coherent multiple soft scattering with the in-medium color charges. Such
scattering leads to calculable modifications of the hadron production cross
section that is evaluated in the framework of the perturbative QCD
factorization approach. Final state medium-induced gluon bremsstrahlung is
arguably the most efficient way of suppressing large transverse momentum
particle production in nucleus-nucleus collisions. The observed hadronic
attenuation, known as jet quenching, can be related to the properties of the
medium, such as density and temperature, and carries valuable information about
the early stages of heavy ion reactions. Non-Abelian energy loss in the
quark-gluon plasma can be studied in much greater detail through the
modification of the two particle back-to-back correlations. Perturbative
calculations give good description of the redistribution of the lost energy in
lower transverse momentum particles and predict significant increase of the
correlation width of away-side di-hadrons. In contrast, energy loss in cold
nuclear matter was found to be small but for large values of Feynman-x is
expected to complement the dynamical higher twist shadowing in experimentally
observable forward rapidity hadron suppression.Comment: Invited plenary talk at the V-th international conference on the
physics and astrophysics of the quark-gluon plasma. 8 pages, 4 figure
Direct photons in d+Au collisions at s_(NN)**(1/2)=200GeV with STAR
Results are presented of an ongoing analysis of direct photon production in
s_(NN)=200GeV deuteron-gold collisions with the STAR experiment at RHIC. A
significant excess of direct photons is observed near mid-rapidity 0<y<1 and
found to be consistent with next-to-leading order pQCD calculations including
the contribution from fragmentation photons.Comment: 4 pages, 4 figures, HotQuarks 200
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