6,335 research outputs found
Density matrix expansion for the MDI interaction
By assuming that the isospin- and momentum-dependent MDI interaction has a
form similar to the Gogny-like effective two-body interaction with a Yukawa
finite-range term and the momentum dependence only originates from the
finite-range exchange interaction, we determine its parameters by comparing the
predicted potential energy density functional in uniform nuclear matter with
what has been usually given and used extensively in transport models for
studying isospin effects in intermediate-energy heavy-ion collisions as well as
in investigating the properties of hot asymmetric nuclear matter and neutron
star matter. We then use the density matrix expansion to derive from the
resulting finite-range exchange interaction an effective Skyrme-like zero-range
interaction with density-dependent parameters. As an application, we study the
transition density and pressure at the inner edge of neutron star crusts using
the stability conditions derived from the linearized Vlasov equation for the
neutron star matter.Comment: 11 pages, 6 figures, version to appear in Phys. Rev.
Triangular flow in heavy ion collisions in a multiphase transport model
We have obtained a new set of parameters in a multiphase transport (AMPT)
model that are able to describe both the charged particle multiplicity density
and elliptic flow measured in Au+Au collisions at center of mass energy
GeV at the Relativistic Heavy Ion Collider (RHIC), although
they still give somewhat softer transverse momentum spectra. We then use the
model to predict the triangular flow due to fluctuations in the initial
collision geometry and study its effect relative to those from other harmonic
components of anisotropic flows on the di-hadron azimuthal correlations in both
central and mid-central collisions.Comment: 7 pages, 9 figures, 1 table, small changes made to the figures and
the text, version to appear in Phys. Rev.
Higher-order anisotropic flows and dihadron correlations in Pb-Pb collisions at TeV in a multiphase transport model
Using a multiphase transport model that includes both initial partonic and
final hadronic scatterings, we have studied higher-order anisotropic flows as
well as dihadron correlations as functions of pseudorapidity and azimuthal
angular differences between trigger and associated particles in Pb-Pb
collisions at TeV. With parameters in the model determined
previously from fitting the measured multiplicity density of mid-pseudorapidity
charged particles in central collisions and their elliptic flow in mid-central
collisions, the calculated higher-order anisotropic flows from the two-particle
cumulant method reproduce approximately those measured by the ALICE
Collaboration, except at small centralities where they are slightly
overestimated. Similar to experimental results, the two-dimensional dihadron
correlations at most central collisions show a ridge structure at the near side
and a broad structure at the away side. The short- and long-range dihadron
azimuthal correlations, corresponding to small and large pseudorapidity
differences, respectively, are studied for triggering particles with different
transverse momenta and are found to be qualitatively consistent with
experimental results from the CMS Collaboration. The relation between the
short-range and long-range dihadron correlations with that induced by
back-to-back jet pairs produced from initial hard collisions is also discussed.Comment: 7 pages, 7 figures, version to appear in Phys. Rev.
Chemical freeze-out in relativistic heavy-ion collisions
One surprising result in relativistic heavy-ion collisions is that the
abundance of various particles measured in experiments is consistent with the
picture that they reach chemical equilibrium at a temperature much higher than
the temperature they freeze out kinetically. Using a multiphase transport model
to study particle production in these collisions, we find that the above result
is due to the constancy of the entropy per particle during the evolution of the
hadronic matter from the chemical to the kinetic freeze-out. We further use a
hadron resonance gas model to illustrate the result from the transport model
study.Comment: 5 pages, 4 figure
Collision energy dependence of elliptic flow splitting between particles and their antiparticles from an extended multiphase transport model
Based on an extended multiphase transport model, which includes mean-field
potentials in both the partonic and hadronic phases, uses the mix-event
coalescence, and respects charge conservation during the hadronic evolution, we
have studied the collision energy dependence of the elliptic flow splitting
between particles and their antiparticles. This extended transport model
reproduces reasonably well the experimental data at lower collision energies
but only describes qualitatively the elliptic flow splitting at higher beam
energies. The present study thus indicates the existence of other mechanisms
for the elliptic flow splitting besides the mean-field potentials and the need
of further improvements of the multiphase transport model.Comment: 8 pages, 6 figure
The effect of triangular flow on di-hadron azimuthal correlations in relativistic heavy ion collisions
Using the AMPT model for relativistic heavy ion collisions, we have studied
the di-hadron azimuthal angular correlations triggered by emitted jets in Au+Au
collisions at center of mass energy GeV and impact
parameter fm. A double-peak structure for the associated particles at the
away side of trigger particles is obtained after subtracting background
correlations due to the elliptic flow. Both the near-side peak and the
away-side double peaks in the azimuthal angular correlations are, however,
significantly suppressed (enhanced) in events of small (large) triangular flow,
which are present as a result of fluctuations in the initial collision
geometry. After subtraction of background correlations due to the triangular
flow, the away-side double peaks change into a single peak with broad shoulders
on both sides. The away side of the di-hadron correlations becomes essentially
a single peak after further subtraction of higher-order flows.Comment: 5 pages, 5 figures, version accepted by Rapid Communication in
Physical Review
XJ-BP: Express Journey Belief Propagation Decoding for Polar Codes
This paper presents a novel propagation (BP) based decoding algorithm for
polar codes. The proposed algorithm facilitates belief propagation by utilizing
the specific constituent codes that exist in the factor graph, which results in
an express journey (XJ) for belief information to propagate in each decoding
iteration. In addition, this XJ-BP decoder employs a novel round-trip message
passing scheduling method for the increased efficiency. The proposed method
simplifies min-sum (MS) BP decoder by 40.6%. Along with the round-trip
scheduling, the XJ-BP algorithm reduces the computational complexity of MS BP
decoding by 90.4%; this enables an energy-efficient hardware implementation of
BP decoding in practice.Comment: submitted to GLOBECOMM 201
Isospin-dependent pion in-medium effects on charged pion ratio in heavy ion collisions
Using results from the chiral perturbation theory for the s-wave interaction
and the delta-resonance model for the p-wave interaction of pions with
nucleons, we have evaluated the spectral functions of pions in asymmetric
nuclear matter with unequal proton and neutron densities. We find that in hot
dense neutron-rich matter the strength of the spectral function of positively
charged pion at low energies is somewhat larger than that of negatively charged
pion. In a thermal model, this isospin-dependent effect slightly reduces the
ratio of negatively charged to positively charged pions that are produced in
heavy ion collisions induced by radioactive beams. Relevance of our results to
the determination of the nuclear symmetry energy from measured ratio of
negatively to positively charged pions produced in heavy ion collisions is
discussed.Comment: 7 pages, 4 figures, pion-nucleon s-wave interaction include
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