110 research outputs found
Hydrodynamical modeling of the deconfinement phase transition and explosive hadronization
Dynamics of relativistic heavy-ion collisions is investigated on the basis of a simple (1+1)-dimensional hydrodynamical model in light-cone coordinates. The main emphasis is put on studying sensitivity of the dynamics and observables to the equation of state and initial conditions. Low sensitivity of pion rapidity spectra to the presence of the phase transition is demonstrated, and some inconsistencies of the equilibrium scenario are pointed out. Possible non-equilibrium effects are discussed, in particular, a possibility of an explosive disintegration of the deconfined phase into quark-gluon droplets. Simple estimates show that the characteristic droplet size should decrease with increasing the collective expansion rate. These droplets will hadronize individually by emitting hadrons from the surface. This scenario should reveal itself by strong non-statistical fluctuations of observables. Critical Point and Onset of Deconfinement 4th International Workshop July 9-13 2007 GSI Darmstadt,German
MCHIT - Monte Carlo model for proton and heavy-ion therapy
We study the propagation of nucleons and nuclei in tissue-like media within a
Monte Carlo Model for Heavy-ion Therapy (MCHIT) based on the GEANT4 toolkit
(version 8.2). The model takes into account fragmentation of projectile nuclei
and secondary interactions of produced nuclear fragments. Model predictions are
validated with available experimental data obtained for water and PMMA phantoms
irradiated by monoenergetic carbon-ion beams. The MCHIT model describes well
(1) the depth-dose distributions in water and PMMA, (2) the doses measured for
fragments of certain charge, (3) the distributions of positron emitting nuclear
fragments produced by carbon-ion beams, and (4) the energy spectra of secondary
neutrons measured at different angles to the beam direction. Radial dose
profiles for primary nuclei and for different projectile fragments are
calculated and discussed as possible input for evaluation of biological dose
distributions. It is shown that at the periphery of the transverse dose profile
close to the Bragg peak the dose from secondary nuclear fragments is comparable
to the dose from primary nuclei.Comment: Talk given at International Conference on Nuclear Data for Science
and Technology ND-2007, Nice, France, April 22-27, 200
Thermodynamics of dense hadronic matter in a parity doublet model
We study thermodynamics of nuclear matter in a two-flavored parity doublet
model within the mean field approximation. Parameters of the model are chosen
to reproduce correctly the properties of the nuclear ground state. The model
predicts two phase transitions in nuclear matter, a liquid-gas phase transition
at normal nuclear density and a chiral transition at higher density. At finite
temperature the pion decay constant exhibits a considerable reduction at
intermediate values of chemical potential, which is traced back to the presence
of the liquid-gas transition, and approaches zero at higher chemical potential
associated with the chiral symmetry restoration. A "transition" from meson-rich
to baryon-rich matter is also discussed.Comment: 7 pages, 4 figure
Nonlinear oscillations of compact stars in the vicinity of the maximum mass configuration
We solve the dynamical GR equations for the spherically symmetric evolution
of compact stars in the vicinity of the maximum mass, for which instability
sets in according to linear perturbation theory. The calculations are done with
the analytical Zeldovich-like EOS P=a(rho-rho_0) and with the TM1
parametrisation of the RMF model. The initial configurations for the dynamical
calculations are represented by spherical stars with equilibrium density
profile, which are perturbed by either (i) an artificially added inward
velocity field proportional to the radial coordinate, or (ii) a rarefaction
corresponding to a static and expanded star. These configurations are evolved
using a one-dimensional GR hydro code for ideal and barotropic fluids.
Depending on the initial conditions we obtain either stable oscillations or the
collapse to a black hole. The minimal amplitude of the perturbation, needed to
trigger gravitational collapse is evaluated. The approximate independence of
this energy on the type of perturbation is pointed out. At the threshold we
find type I critical behaviour for all stellar models considered and discuss
the dependence of the time scaling exponent on the baryon mass and EOS.Comment: 15 pages, 8 figures, accepted for publication in EP
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