11 research outputs found
Studies of parton thermalization at RHIC
We consider the evolution of a parton system which is formed in the central
region just after a relativistic heavy ion collision. The parton consist of
mostly gluons, minijets, which are produced by elastic scattering between
constituent partons of the colliding nuclei. We assume the system can be
described by a semi-classical Boltzmann transport equation, which we solve by
means of the test particle Monte-Carlo method including retardation. The
partons proliferate via secondary radiative processes until the
thermalization is reached for some assumptions. The extended system is
thermalized at about fm/ with MeV and stays in equilibrium
for about 2 fm/ with breaking temperature MeV in the rapidity
central region.Comment: 14 page
Suppression of High Transverse Momentum Spectra in Au+Au Collisions at RHIC
Au+Au, A GeV measurements at RHIC, obtained with the PHENIX,
STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of neutral
pion production, relative to an appropriately normalized NN level. For central
collisions and vanishing pseudo-rapidity these experiments exhibit suppression
in charged meson production, especially at medium to large transverse momenta.
In the PHENIX experiment similar behavior has been reported for
spectra.
In a recent work on the simpler D+Au interaction, to be considered perhaps as
a tune-up for Au+Au, we reported on a pre-hadronic cascade mechanism which
explains the mixed observation of moderately reduced suppression at
higher pseudo-rapidity as well as the Cronin enhancement at mid-rapidity. Here
we present the extension of this work to the more massive ion-ion collisions.
Our major thesis is that much of the suppression is generated in a late stage
cascade of colourless pre-hadrons produced after an initial short-lived
coloured phase. We present a pQCD argument to justify this approach and to
estimate the time duration of this initial phase. Of essential
importance is the brevity in time of the coloured phase existence relative to
that of the strongly interacting pre-hadron phase. The split into two phases is
of course not sharp in time, but adequate for treating the suppression of
moderate and high mesons.Comment: 19 pages, 10 figure
Hydrodynamic afterburner for the CGC at RHIC
Firstly, we give a short review about the hydrodynamic model and its
application to the elliptic flow phenomena in relativistic heavy ion
collisions. Secondly, we show the first approach to construct a unified model
for the description of the dynamics in relativistic heavy ion collisions.Comment: 15 pages, 7 figures, invited talk presented at "Hot Quarks 2004",
July 18-24, 2004, Taos Valley, NM, US
Cronin Effect and High-p_T Suppression in pA Collisions
We review the predictions of the theory of Color Glass Condensate for gluon
production cross section in p(d)A collisions. We demonstrate that at moderate
energies, when the gluon production cross section can be calculated in the
framework of McLerran-Venugopalan model, it has only partonic level Cronin
effect in it. At higher energies/rapidities corresponding to smaller values of
Bjorken x quantum evolution becomes important. The effect of quantum evolution
at higher energies/rapidities is to introduce suppression of high-p_T gluons
slightly decreasing the Cronin enhancement. At still higher energies/rapidities
quantum evolution leads to suppression of produced gluons at all values of p_T.Comment: 32 pages, 8 figures, v2: extended and improved discussion, references
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CGC, QCD Saturation and RHIC data (Kharzeev-Levin-McLerran-Nardi point of view)
This is the talk given at the Workshop:"Focus on Multiplicitioes", Bari,
Italy, 17-19 June,2004.. In this talk, we are going to discuss ion-ion and
deuteron - nucleus RHIC data and show that they support, if not more, the idea
of the new QCD phase: colour glass condensate with saturated parton density. .Comment: 26 pages with 33 figure
BFKL Pomeron calculus: solution to equations for nucleus-nucleus scattering in the saturation domain
The Colour Glass Condensate: An Introduction
In these lectures, the authors develop the theory of the Colour Glass Condensate. This is the matter made of gluons in the high density environment characteristic of deep inelastic scattering or hadron-hadron collisions at very high energy. The lectures are self contained and comprehensive. They start with a phenomenological introduction, develop the theory of classical gluon fields appropriate for the Colour Glass, and end with a derivation and discussion of the renormalization group equations which determine this effective theory