663 research outputs found
Beam Energy Evolution of HBT Systematics at the AGS
We present preliminary results of the first pion interferometry (HBT)
excitation function at intermediate AGS energies. The beam energy evolution of
the correlations' dependence on mT, centrality, and emission angle with respect
to the reaction plane are discussed. Comparisons with predictions of the RQMD
cascade model are made.Comment: to appear in proceedings of Quark Matter '9
Influence of the pion-nucleon interaction on the collective pion flow in heavy ion reactions
We investigate the influence of the real part of the in-medium pion optical
potential on the pion dynamics in intermediate energy heavy ion reactions at 1
GeV/A. For different models, i.e. a phenomenological model and the
--hole model, a pionic potential is extracted from the dispersion
relation and used in Quantum Molecular Dynamics calculations. In addition with
the inelastic scattering processes we thus take care of both, real and
imaginary part of the pion optical potential. A strong influence of the real
pionic potential on the pion in-plane flow is observed. In general such a
potential has the tendency to reduce the anticorrelation of pion and nucleon
flow in non-central collisions.Comment: 12 pages Latex, 4 PS-figure
Asymmetric Colliding Nuclear Matter Approach in Heavy Ion Collisions
The early stage of a heavy ion collision is governed by local non-equilibrium
momentum distributions which have been approximated by colliding nuclear matter
configurations, i.e. by two Lorentz elongated Fermi ellipsoids. This approach
has been extended from the previous assumption of symmetric systems to
asymmetric 2-Fermi sphere configurations, i.e. to different densities. This
provides a smoother transition from the limiting situation of two
interpenetrating currents to an equilibrated system. The model is applied to
the dynamical situations of heavy ion collisions at intermediate energies
within the framework of relativistic transport (RBUU) calculations. We find
that the extended colliding nuclear matter approach is more appropriate to
describe collective reaction dynamics in terms of flow observables, in
particular, for the elliptic flow at low energies.Comment: 21 pages, 8 figures, accepted for publication in Nuclear Physics
Effect of Chiral Symmetry Restoration on Pentaquark Mass and Width at Finite Temperature and Density
We investigate the effect of chiral phase transition on the pentaquark
mass and width at one-loop level of coupling at finite
temperature and density. The behavior of the mass, especially the width in
hadronic medium is dominated by the characteristics of chiral symmetry
restoration at high temperature and high density. The mass and width shifts of
positive-parity are much larger than that of negative-parity one,
which may be helpful to determine the parity of in high energy
nuclear collisions.Comment: 7 pages, 5 figure
PHENIX Highlights
Recent highlights of measurements by the PHENIX experiment at RHIC are
presented.Comment: 8 pages, 9 figures. Talk at Quark Matter 200
Baryon flow from SIS to AGS energies
We analyze the baryon sideward and elliptic flow from SIS (0.25 2 A
GeV) to AGS (2 GeV) energies for Au + Au collisions in the
relativistic transport model RBUU that includes all baryon resonances up to a
mass of 2 GeV as well as string degrees of freedom for the higher mass
continuum. There are two factors which dominantly determine the baryon flow at
these energies: the momentum dependence of the scalar and vector potentials and
the resonance-string degrees of freedom. We fix the explicit momentum
dependence of the nucleon-meson couplings within the NL3 parameter set by the
nucleon optical potential up to 1 GeV of kinetic energy. When assuming the
optical potential to vanish identically for GeV we
simultaneously reproduce the sideward flow data of the FOPI, EOS, E895 and E877
collaborations, the elliptic flow data of the EOS, E895 and E877
collaborations, and approximately the rapidity and transverse mass distribution
of protons at AGS energies. The gradual change from hadronic to string degrees
of freedom with increasing bombarding energy can be viewed as a transition from
{\it hadronic} to {\it string} matter, i.e. a dissolution of hadrons.Comment: 13 pages, 4 figures, corrected the figures and the tex
Anisotropic flow in 4.2A GeV/c C+Ta collisions
Anisotropic flow of protons and negative pions in 4.2A GeV/c C+Ta collisions
is studied using the Fourier analysis of azimuthal distributions. The protons
exhibit pronounced directed flow. Directed flow of pions is positive in the
entire rapidity interval and indicates that the pions are preferentially
emitted in the reaction plane from the target to the projectile. The elliptic
flow of protons and negative pions is close to zero. Comparison with the
quark-gluon-string model (QGSM) and relativistic transport model (ART 1.0) show
that they both yield a flow signature similar to the experimental data.Comment: 4 pages, 3 figures, Accepted for publication in Phys. Rev.
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