1,522 research outputs found
Evolution of shower parton distributions in a jet from quark recombination model
The evolution of shower parton distributions in a jet is investigated in the
framework of quark recombination model. The distributions are parameterized and
the dependence of the parameters is given by polynomials of for
a wide range of .Comment: 5 pages in RevTeX, 3 figures in ep
Void Analysis of Hadronic Density Fluctuations at Phase Transition
The event-to-event fluctuations of hadron multiplicities are studied for a
quark system undergoing second-order phase transition to hadrons. Emphasis is
placed on the search for an observable signature that is realistic for
heavy-ion collisions. It is suggested that in the 2-dimensional y-phi space the
produced particles selected in a very narrow p_T window may exhibit clustering
patterns even when integrated over the entire emission time. Using the Ising
model to simulate the critical phenomenon and taking into account a p_T
distribution that depends on the emission time, we study in the framework of
the void analysis proposed earlier and find scaling behavior. The scaling
exponents turn out to be larger than the ones found before for pure
configurations without mixing. The signature is robust in that it is
insensitive to the precise scheme of simulating time evolution. Thus it should
reveal whether or not the dense matter created in heavy-ion collisions is a
quark-gluon plasma before hadronization.Comment: 11 pages in LaTeX + 6 figures in p
Parton Branching in Color Mutation Model
The soft production problem in hadronic collisions as described in the
eikonal color mutation branching model is improved in the way that the initial
parton distribution is treated. Furry branching of the partons is considered as
a means of describing the nonperturbative process of parton reproduction in
soft interaction. The values of all the moments, and , for q=2,...,5,
as well as their energy dependences can be correctly determined by the use of
only two parameters.Comment: 8 pages (LaTeX) + 2 figures (ps files), submitted to Phys. Rev.
Critical Behavior of Hadronic Fluctuations and the Effect of Final-State Randomization
The critical behaviors of quark-hadron phase transition are explored by use
of the Ising model adapted for hadron production. Various measures involving
the fluctuations of the produced hadrons in bins of various sizes are examined
with the aim of quantifying the clustering properties that are universal
features of all critical phenomena. Some of the measures involve wavelet
analysis. Two of the measures are found to exhibit the canonical power-law
behavior near the critical temperature. The effect of final-state randomization
is studied by requiring the produced particles to take random walks in the
transverse plane. It is demonstrated that for the measures considered the
dependence on the randomization process is weak. Since temperature is not a
directly measurable variable, the average hadronic density of a portion of each
event is used as the control variable that is measurable. The event-to-event
fluctuations are taken into account in the study of the dependence of the
chosen measures on that control variable. Phenomenologically verifiable
critical behaviors are found and are proposed for use as a signature of
quark-hadron phase transition in relativistic heavy-ion collisions.Comment: 17 pages (Latex) + 24 figures (ps file), submitted to Phys. Rev.
Universal behavior of multiplicity differences in quark-hadron phase transition
The scaling behavior of factorial moments of the differences in
multiplicities between well separated bins in heavy-ion collisions is proposed
as a probe of quark-hadron phase transition. The method takes into account some
of the physical features of nuclear collisions that cause some difficulty in
the application of the usual method. It is shown in the Ginzburg-Landau theory
that a numerical value of the scaling exponent can be determined
independent of the parameters in the problem. The universality of
characterizes quark-hadron phase transition, and can be tested directly by
appropriately analyzed data.Comment: 15 pages, including 4 figures (in epsf file), Latex, submitted to
Phys. Rev.
Erraticity of Rapidity Gaps
The use of rapidity gaps is proposed as a measure of the spatial pattern of
an event. When the event multiplicity is low, the gaps between neighboring
particles carry far more information about an event than multiplicity spikes,
which may occur very rarely. Two moments of the gap distrubiton are suggested
for characterizing an event. The fluctuations of those moments from event to
event are then quantified by an entropy-like measure, which serves to describe
erraticity. We use ECOMB to simulate the exclusive rapidity distribution of
each event, from which the erraticity measures are calculated. The dependences
of those measures on the order of of the moments provide single-parameter
characterizations of erraticity.Comment: 10 pages LaTeX + 5 figures p
Particle correlations at RHIC from parton coalescence dynamics -- first results
A new dynamical approach that combines covariant parton transport theory with
hadronization channels via parton coalescence and fragmentation is applied to
Au+Au at RHIC. Basic consequences of the simple coalescence formulas, such as
elliptic flow scaling and enhanced proton/pion ratio, turn out to be rather
sensitive to the spacetime aspects of coalescence dynamics.Comment: Contribution to Quark Matter 2004 (January 11-17, 2004, Oakland, CA).
4 pages, 2 EPS figs, IOP style fil
Multiplicity Distributions of Squeezed Isospin States
Multiplicity distributions of neutral and charged particles arising from
squeezed coherent states are investigated. Projections onto global isospin
states are considered. We show how a small amount of squeezing can
significantly change the multiplicity distributions. The formalism is proposed
to describe the phenomenological properties of neutral and charged particles
anomalously produced in hadronic and nuclear collisions at very high energies.Comment: 17 pages, 6 figures sent upon request ([email protected]
On Nonlinear Diffusion with Multiplicative Noise
Nonlinear diffusion is studied in the presence of multiplicative noise. The
nonlinearity can be viewed as a ``wall'' limiting the motion of the diffusing
field. A dynamic phase transition occurs when the system ``unbinds'' from the
wall. Two different universality classes, corresponding to the cases of an
``upper'' and a ``lower'' wall, are identified and their critical properties
are characterized. While the lower wall problem can be understood by applying
the knowledge of linear diffusion with multiplicative noise, the upper wall
problem exhibits an anomaly due to nontrivial dynamics in the vicinity of the
wall. Broad power-law distribution is obtained throughout the bound phase.Comment: 4 pages, LaTeX, text and figures also available at
http://matisse.ucsd.edu/~hw
Quark Coalescence for Charmed Mesons in Ultrarelativistic Heavy-Ion Collisions
We investigate effects of charm-quark interactions in a Quark-Gluon Plasma on
the production of and mesons in high-energy heavy-ion collisions.
Employing a previously constructed coalescence model that successfully
reproduces the transverse momentum () spectra and elliptic flow
() of light hadrons at RHIC from underlying light-quark distributions
at the phase transition temperature , -meson and spectra
are evaluated. For the charm-quark distributions, we consider two limiting
scenarios: (i) {\em no} rescattering, corresponding to perturbative QCD spectra
and (ii) {\em complete} thermalization including transverse expansion. With the
-meson spectra acquiring a minimal inherited from their light-quark
content, the corresponding semileptonic decay spectra of single electrons are
found to practically preserve the of the parent particles, exhibiting
marked differences between the pQCD and thermal scenarios for GeV.
Likewise, the -spectra and yields of 's differ appreciably in the
two scenarios.Comment: 6 pages, 4 figures, version published in PLB with updated figure
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