202 research outputs found
Space-time evolution and HBT analysis of relativistic heavy ion collisions in a chiral SU(3) x SU(3) model
The space-time dynamics and pion-HBT radii in central heavy ion-collisions at
CERN-SPS and BNL-RHIC are investigated within a hydrodynamic simulation. The
dependence of the dynamics and the HBT-parameters on the EoS is studied with
different parametrisations of a chiral SU(3) sigma-omega model. The
selfconsistent collective expansion includes the effects of effective hadron
masses, generated by the nonstrange and strange scalar condensates. Different
chiral EoS show different types of phase transitions and even a crossover. The
influence of the order of the phase transition and of the difference in the
latent heat on the space-time dynamics and pion-HBT radii is studied. A small
latent heat, i.e. a weak first-order chiral phase transition, or even a smooth
crossover leads to distinctly different HBT predictions than a strong first
order phase transition. A quantitative description of the data, both at SPS
energies as well as at RHIC energies, appears difficult to achieve within the
ideal hydrodynamical approach using the SU(3) chiral EoS. A strong first-order
quasi-adiabatic chiral phase transition seems to be disfavored by the pion-HBT
data from CERN-SPS and BNL-RHIC
System-size dependence of the pion freeze-out volume as a potential signature for the phase transition to a Quark Gluon Plasma
Hanburry-Brown-Twiss (HBT) correlation functions and radii of negatively
charged pions from C+C, Si+Si, Cu+Cu, and In+In at lower RHIC/SPS energies are
calculated with the UrQMD transport model and the CRAB analyzing program. We
find a minimum in the excitation function of the pion freeze-out volume at low
transverse momenta and around GeV which can be related to
the transition from hadronic to string matter (which might be interpreted as a
pre-cursor of the QGP). The existence of the minimum is explained by the
competition of two mechanisms of the particle production, resonance decays and
string formation/fragmentation.Comment: 12 pages, 4 fig
Size Matters: Origin of Binomial Scaling in Nuclear Fragmentation Experiments
The relationship between measured transverse energy, total charge recovered
in the detector, and size of the emitting system is investigated. Using only
very simple assumptions, we are able to reproduce the observed binomial
emission probabilities and their dependences on the transverse energy.Comment: 14 pages, including 4 figure
Subjective Expected Utility with Non-Increasing Risk Aversion
It is shown that assumptions about risk aversion, usually studied under the pre-supposition of expected utility maximization, have a surprising extra merit at an earlier stage of the measurement work: together with the sure-thing principle, these assumptions imply subjective expected utility maximization for monotonic continuous weak orders
Nonequilibrium fluid-dynamics in the early stage of ultrarelativistic heavy-ion collisions
To describe ultrarelativistic heavy-ion collisions we construct a three-fluid
hydrodynamical model. In contrast to one-fluid hydrodynamics, it accounts for
the finite stopping power of nuclear matter, i.e. for nonequilibrium effects in
the early stage of the reaction. Within this model, we study baryon dynamics in
the BNL-AGS energy range. For the system Au+Au we find that kinetic equilibrium
between projectile and target nucleons is established only after a time
. Observables which are
sensitive to the early stage of the collision (like e.g. nucleon flow)
therefore differ considerably from those calculated in the one-fluid model.Comment: 36 pages, Late
Hadronic freeze-out following a first order hadronization phase transition in ultrarelativistic heavy-ion collisions
We analyze the hadronic freeze-out in ultra-relativistic heavy ion collisions
at RHIC in a transport approach which combines hydrodynamics for the early,
dense, deconfined stage of the reaction with a microscopic non-equilibrium
model for the later hadronic stage at which the hydrodynamic equilibrium
assumptions are not valid. With this ansatz we are able to self-consistently
calculate the freeze-out of the system and determine space-time hypersurfaces
for individual hadron species. The space-time domains of the freeze-out for
several hadron species are found to be actually four-dimensional, and differ
drastically for the individual hadrons species. Freeze-out radii distributions
are similar in width for most hadron species, even though the Omega-baryon is
found to be emitted rather close to the phase boundary and shows the smallest
freeze-out radii and times among all baryon species. The total lifetime of the
system does not change by more than 10% when going from SPS to RHIC energies.Comment: 11 pages, 4 eps-figures included, revised versio
Imaging Sources with Fast and Slow Emission Components
We investigate two-proton correlation functions for reactions in which fast
dynamical and slow evaporative proton emission are both present. In such cases,
the width of the correlation peak provides the most reliable information about
the source size of the fast dynamical component. The maximum of the correlation
function is sensitive to the relative yields from the slow and fast emission
components. Numerically inverting the correlation function allows one to
accurately disentangle fast dynamical from slow evaporative emission and
extract details of the shape of the two-proton source.Comment: 13 pages, 4 figure
Social Support and Health: A Theoretical Formulation Derived from King's Conceptual Framework
This article describes the development and initial empirical testing of a theoretical formulation of social support, family, health, and child health derived from Imogene King's conceptual framework for nursing. A correlational design was used to test the formulation with 103 families who have children with diabetes mellitus. Three hypotheses were sup ported : parents' social support had a direct and positive effect on family health, parents' social support and child's social support were positively related, and illness factors had a direct and negative effect on child health. Both the supported and unsupported hypotheses are discussed in terms of the present substantive knowledge base and evidence of validity for King's framework. Direction for further theory development and research are identified.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68995/2/10.1177_089431848900200309.pd
The Bose-Einstein effect in Monte-Carlo generators: weight methods
We present a method which incorporates the Bose-Einstein effect into Monte
Carlo generators for multiple production by weighting the events. Various
aspects of weight calculations are discussed in detail. We show that our method
allows to describe reasonably well a sample of data and we outline the future
tests and applications.Comment: Latex, 10 pages including 4 .eps figure
Last Call for RHIC Predictions
This paper contains the individual contributions of all speakers of the
session on 'Last Call for RHIC Predictions' at Quark Matter 99, and a summary
by the convenor.Comment: 56 pages, psfig, epsf, epsfig, graphicx style files required,
Proceedings of the XIV Int. Conf. on Nucleus-Nucleus Collisions, Quark Matter
99, Torino, Italy, May 10 - 15, 1999. Typographical mistakes corrected and
figure numbers change
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