713 research outputs found
Heavy Ion Collisions and the Density Dependence of the Local Mean Field
We study the effect of the density dependence of the scalar and the vector
part of the nucleonic self-energy in Relativistic Quantum Molecular Dynamics
(RQMD) on observables like the transversal flow and the rapidity distribution.
The stability of nuclei in RQMD is greatly improved if the density dependence
is included in the self-energies compared to a calculation assuming always
saturation density of nuclear matter. Different approaches are studied: The
main results are calculated with self-energies extracted from a
Dirac-Br\"uckner-Hartree-Fock G-matrix of a one boson exchange model, i.e. the
Bonn potential. These results are compared with those obtained by a
generalization of static Skyrme force, with calculations in the simple linear
Walecka model and results of the Br\"uckner-Hartree-Fock G-matrix of the Reid
soft core potential. The transversal flow is very sensitive to these different
approaches. A comparison with the data is given.Comment: LaTex-file, 13 pages, 5 figures (available upon request), submitted
to Nuclear Physics
Lateral distribution of high energy hadrons and gamma ray in air shower cores observed with emulsion chambers
A high energy event of a bundle of electrons, gamma rays and hadronic gamma rays in an air shower core were observed. The bundles were detected with an emulsion chamber with thickness of 15 cm lead. This air shower is estimated to be initiated with a proton with energy around 10 to the 17th power to 10 to the 18th power eV at an altitude of around 100 gmc/2. Lateral distributions of the electromagnetic component with energy above 2 TeV and also the hadronic component of energy above 6 TeV of this air shower core were determined. Particles in the bundle are produced with process of the development of the nuclear cascade, the primary energy of each interaction in the cascade which produces these particles is unknown. To know the primary energy dependence of transverse momentum, the average products of energy and distance for various average energies of secondary particles are studied
Probing the nuclear equation of state by production in heavy ion collisions
The dependence of production on the nuclear equation of state is
investigated in heavy ion collisions. An increase of the excitation function of
multiplicities obtained in heavy () over light () systems
when going far below threshold which has been observed by the KaoS
Collaboration strongly favours a soft equation of state. This observation holds
despite of the influence of an in-medium kaon potential predicted by effective
chiral models which is necessary to reproduce the experimental yields.Comment: 4 pages Revtex, 4 PS figures, to appear in Phys. Rev. Let
The nuclear equation of state probed by production in heavy ion collisions
The dependence of production on the nuclear equation of state is
investigated in heavy ion collisions. An increase of the excitation function of
multiplicities obtained in heavy () over light () systems
when going far below threshold which has been observed by the KaoS
Collaboration strongly favours a soft equation of state. This observation holds
despite of the influence of an in-medium kaon potential predicted by effective
chiral models which is necessary to reproduce the experimental yields.
Phase space effects are discussed with respect to the excitation
function.Comment: 14 pages Revtex, 6 figures, Proceedings to the XXXIX Interantional
Winter Meeting on Nuclear Physics, Bormio, Italy, 200
Does the effective Lagrangian for low-energy QCD scale?
QCD is not an approximately scale invariant theory. Hence a dilaton field is
not expected to provide a good description of the low-energy dynamics
associated with the gluon condensate. Even if such a field is introduced, it
remains almost unchanged in hadronic matter at normal densities. This is
because the large glueball mass together with the size of the phenomenological
gluon condensate ensure that changes to that condensate are very small at such
densities. Any changes in hadronic masses and decay constants in matter
generated by that condensate will be much smaller that those produced directly
by changes in the quark condensate. Hence masses and decay constants are not
expected to display a universal scaling.Comment: 7 pages (RevTeX), MC/TH 94/0
Study of in-medium meson properties in Ap, pA and AA collisions
We propose to investigate the in-medium properties of vector mesons
at the normal nuclear density in Ap(pA) collisions and at higher density in AA
collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap
kinematics will permit us to study the meson production in a wide
momentum interval included the not yet explored range of small meson momenta
relative to the projectile nuclei where the mass modification effect in nuclear
matter is expected to be the strongest. Momentum dependence of the in-medium
meson width will be studied in the traditional pA kinematics. We
intend to use the electromagnetic calorimeter for reconstruction of the
meson invariant mass by detecting photons from the decay. The model calculations and simulations with
RQMD generator show feasibility of the proposed experiment. Available now
intensity of the ion beams provides a possibility to collect large statistics
and make decisive conclusion about the meson properties at density of
normal nuclei. At the second stage of the investigation the meson
properties will be studied in AA collisions at higher density. Interpretation
of these measurements will be based on the results obtained in Ap(pA)
interactions. Further investigation of the in-medium properties of light
unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where
higher ion energies will be accessible in near future.Comment: 26 pages, 10 figures, 2 table
- nucleus relativistic mean field potentials consistent with kaonic atoms
atomic data are used to test several models of the nucleus
interaction. The t() optical potential, due to coupled channel
models incorporating the (1405) dynamics, fails to reproduce these
data. A standard relativistic mean field (RMF) potential, disregarding the
(1405) dynamics at low densities, also fails. The only successful
model is a hybrid of a theoretically motivated RMF approach in the nuclear
interior and a completely phenomenological density dependent potential, which
respects the low density theorem in the nuclear surface region. This best-fit
optical potential is found to be strongly attractive, with a depth of 180
\pm 20 MeV at the nuclear interior, in agreement with previous phenomenological
analyses.Comment: revised, Phys. Rev. C in pres
Elastic e-d Scattering Data and the Deuteron Wave Function
What range of momentum components in the deuteron wave function are available
e d elastic scattering data sensitive to ? This question is addressed within
the context of a model calculation of the deuteron form factors, based on
realistic interactions and currents. It is shown that the data on the ,
, and observables at fm essentially probe
momentum components up to .Comment: 5 figure
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