28 research outputs found
Quantifying Baryon Stopping in High Energy Nuclear Collisions
We propose a numerical definition for baryon stopping in relativistic heavy
ion collisions that is obtainable from final hadron rapidity distributions as
well as from bremsstrahlung measurements. Thus a new channel of communication
is opened between the two methods.Comment: latex 9 pages, 2 embedded PS figure
Condensation of a Strongly Interacting Parton Plasma into a Hadron Gas in High Energy Nuclear Collisions
We examine the effects of color screening on the transition of a parton
plasma into a hadron gas at RHIC energies. It is found that as expected, color
screening posed itself as a significant barrier for hadronization.
Parton-hadron conversion would therefore be delayed and prolonged when compared
to that occuring in a vacuum. Due to the on-going expansion, the resulting
hadron densities are lowered. Parton equilibration is also shown to be
seriously disrupted in the process.Comment: 4 pages, 2 embedded EPS figures, talk presented at Quark Matter'99,
Torino, Ital
Color Octet Contribution in Exclusive P-Wave Charmonium Decay
Recent advances in our understanding of the higher-wave quarkonia have
generated much interests in quarkonium physics. However most are devoted to
inclusive decays and productions. Experimental data of several two-body
exclusive decay channels of P-wave charmonia such as \pi \pi and p \bar p are
available and some have recently been re-measured by the BES collaboration. It
is not clear from the outset that color octet is needed for these exclusive
channels. Indeed only color singlet has been used in the past and reasonable
agreement with data was found. Contrary to these old results, we provide
theoretical arguments for the inclusion of color octet and perform explicit
calculations to back this up.Comment: 6 pages using espcrc2.sty, contribution to the 4th Int. Conference on
Hyperons, Charm and Beauty Hadrons, Valencia, June 200
Two-Loop Self-Energy and Multiple Scattering at Finite Temperature
One and two loop self-energies are worked out explicitly for a heavy scalar
field interacting weakly with a light self-interacting scalar field at finite
temperature. The ring/daisy diagrams and a set of necklace diagrams can be
summed simultaneously. This simple model serves to illustrate the connection
between multi-loop self-energy diagrams and multiple scattering in a medium.Comment: 15 pages including 7 figures; v2. with appendix added, accepted by
PR
Baryonic coherent state formation from small domain disoriented chiral condensates
Rare hyperon yields such as the Omega and AntiOmega in heavy ion collision
experiments are hard to be reproduced by numerical models. This, in combination
with the thermal fit to SPS data, seems to call for a new production mechanism
beyond the usual ones. Small domain disoriented chiral condensates (DCC) were
proposed to be such a source of rare hyperons through skyrmion formation at the
chiral phase transition. Here skyrmions are treated as coherent states of
baryons on a compact manifold so that the distribution of baryons produced from
a skyrmion can be known. From this more refined treatment, the number of
topological defects produced are more than doubled to 30 or more and the domain
size at the SPS is found to be even smaller than before at 1.1--1.5 fm. IT IS
IMPERATIVE THEREFORE NOT TO USE ONLY PION DISTRIBUTION BUT OTHER MEANS FOR
OBSERVING DCC.Comment: Talk presented at Quark Matter 2002, Nantes, France, July 2002, to
appear in the proceeding
B_c Meson Production in Nuclear Collisions at RHIC
We study quantitatively the formation and evolution of B_c bound states in a
space-time domain of deconfined quarks and gluons (quark-gluon plasma, QGP). At
the Relativistic Heavy Ion Collider (RHIC) one expects for the first time that
typical central collisions will result in multiple pairs of heavy (in this case
charmed) quarks. This provides a new mechanism for the formation of heavy
quarkonia which depends on the properties of the deconfined region. We find
typical enhancements of about 500 fold for the B_c production yields over
expectations from the elementary coherent hadronic B_c-meson production
scenario. The final population of bound states may serve as a probe of the
plasma phase parameters.Comment: 9 Pages, 11 Postscript Figure
Scattering amplitudes at finite temperature
We present a simple set of rules for obtaining the imaginary part of a self
energy diagram at finite temperature in terms of diagrams that correspond to
physical scattering amplitudes.Comment: 23 pages in Revtex, with 33 eps-figure
Soft Photon Production Rate in Resummed Perturbation Theory of High Temperature QCD
We calculate the production rate of soft real photons from a hot quark --
gluon plasma using Braaten -- Pisarski's perturbative resummation method. To
leading order in the QCD coupling constant we find a logarithmically
divergent result for photon energies of order , where is the plasma
temperature. This divergent behaviour is due to unscreened mass singularities
in the effective hard thermal loop vertices in the case of a massless external
photon.Comment: 13 pages (2 figures not included), PLAINTEX, LPTHE-Orsay 93/46, BI-TP
93/5
Thermal and chemical equilibration in a gluon plasma
We show the evolution of a gluon plasma towards equilibrium starting at some
early moment when the momentum distribution in the central region is
momentaneously isotropic. Using HIJING results for Au+Au collision as initial
input, we consider thermalization and chemical equilibration simultaneously at
both LHC and RHIC energies. Thermalization is shown to be driven chiefly by
inelastic process in our scenario contradicting common assumption that this is
the role of elastic process. We argue that only the inelastic dominancy depends
on the initial conditions but not the dominance itself.Comment: 14 pages + 4 postscript figures, latex2e file, final version to
appear in Nucl. Phys.
Extension of the JIMWLK Equation in the Low Gluon Density Region
It has recently been realized that the Balitsky-JIMWLK equations have serious
shortcomings as equations to be used in small-x evolution near the unitarity
limit. A recent generalization of the Balitsky equations has been given which
corrects these shortcomings. In this paper we present an equivalent discussion,
but in terms of the JIMWLK equation where we show that a new (fourth order
functional derivative) term should be included. We also present a stochastic
version of the new equation which, however, has some unusual mathematical
aspects which are not as yet well understood.Comment: 23 pages, 1 figure, corrected typos, corrected references, published
versio