7,068 research outputs found
Multiphase transport model for heavy ion collisions at RHIC
Using a multiphase transport model (AMPT) with both partonic and hadronic
interactions, we study the multiplicity and transverse momentum distributions
of charged particles such as pions, kaons and protons in central Au+Au
collisions at RHIC energies. Effects due to nuclear shadowing and jet quenching
on these observables are also studied. We further show preliminary results on
the production of multistrange baryons from the strangeness-exchange reactions
during the hadronic stage of heavy ion collisions.Comment: 4 pages, 4 figures, espcrc1.sty included, presented at 15th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(QM2001), Long Island, New York, January 200
NNVA: Neural Network Assisted Visual Analysis of Yeast Cell Polarization Simulation
Complex computational models are often designed to simulate real-world
physical phenomena in many scientific disciplines. However, these simulation
models tend to be computationally very expensive and involve a large number of
simulation input parameters which need to be analyzed and properly calibrated
before the models can be applied for real scientific studies. We propose a
visual analysis system to facilitate interactive exploratory analysis of
high-dimensional input parameter space for a complex yeast cell polarization
simulation. The proposed system can assist the computational biologists, who
designed the simulation model, to visually calibrate the input parameters by
modifying the parameter values and immediately visualizing the predicted
simulation outcome without having the need to run the original expensive
simulation for every instance. Our proposed visual analysis system is driven by
a trained neural network-based surrogate model as the backend analysis
framework. Surrogate models are widely used in the field of simulation sciences
to efficiently analyze computationally expensive simulation models. In this
work, we demonstrate the advantage of using neural networks as surrogate models
for visual analysis by incorporating some of the recent advances in the field
of uncertainty quantification, interpretability and explainability of neural
network-based models. We utilize the trained network to perform interactive
parameter sensitivity analysis of the original simulation at multiple
levels-of-detail as well as recommend optimal parameter configurations using
the activation maximization framework of neural networks. We also facilitate
detail analysis of the trained network to extract useful insights about the
simulation model, learned by the network, during the training process.Comment: Published at IEEE Transactions on Visualization and Computer Graphic
Progress Towards Determining the Density Dependence of the Nuclear Symmetry Energy Using Heavy-Ion Reactions
The latest development in determining the density dependence of the nuclear
symmetry energy using heavy-ion collisions is reviewed. Within the IBUU04
version of an isospin- and momentum-dependent transport model using a modified
Gogny effective interaction, recent experimental data from NSCL/MSU on isospin
diffusion are found to be consistent with a nuclear symmetry energy of
at subnormal densities.
Predictions on several observables sensitive to the density dependence of the
symmetry energy at supranormal densities accessible at GSI and the planned Rare
Isotope Accelerator (RIA) are also made.Comment: 10 pages. Talk given at the 21st Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, USA, Feb. 5-12, 2005. To appear in Heavy-Ion Physics
(2005
Phi meson production in relativistic heavy ion collisions
Within a multiphase transport model we study phi meson production in
relativistic heavy ion collisions from both superposition of initial multiple
proton-proton interactions and the secondary collisions in the produced
hadronic matter. The yield of phi mesons is then reconstructed from their
decaying product of either the kaon-antikaon pairs or the dimuon pairs. Since
the kaon-antikaon pairs at midrapidity with low transverse momenta are
predominantly rescattered or absorbed in the hadronic medium, they can not be
used to reconstruct the phi meson and lead thus to a smaller reconstructed phi
meson yield than that reconstructed from the dimuon channel. With in-medium
mass modifications of kaons and phi mesons, the phi yield from dimuons is
further enhanced compared to that from the kaon-antikaon pairs. The model
result is compared with the experimental data at the CERN/SPS and RHIC energies
and its implications to quark-gluon plasma formation are discussed.Comment: Revised version, to appear in Nucl. Phys.
Chiral condensate in nuclear matter with vacuum corrections
Within the relativistic Hartree approach using a Lagrangian with
density-dependent parameters respecting the chiral limit, it is found that the
vacuum corrections from the nucleon Dirac sea soften the equation of state and
favor the chiral symmetry restoration at high densities.Comment: 12 page
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