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L. M. Satarov

Publications and source records attributed to L. M. Satarov.

44 records · Page 3Linked to original sources

Influence of irradiation on the space-time structure of shock waves

The long-range energy deposition by heavy-ion beams makes new types of shock wave experiments possible in the laboratory. We have investigated a situation that is of relevance to supernova dynamics in astrophysics, where a shock wave is irradiated by a flux of neutrinos depositing energy throughout the shock wave and surrounding matter, thus changing the behaviour of the running shock. We have carried out fluid-dynamical simulations to study generic features of stimulated shock waves. First we consider an idealized case assuming uniform energy deposition into a planar shock wave propagating through an ideal gas. Then we investigate more realistic situations realizable in laboratory experiments with heavy-ion beams. We have found that energy deposition leads to two important effects: acceleration of the shock front and decay of the shock strength. The possibility of laboratory experiments is briefly discussed.

astro-ph↗

Strange quark stars within the Nambu-Jona-Lasinio model

We investigate the properties of charge-neutral $β$-equilibrium cold quark matter within the Nambu-Jona-Lasinio model. The calculations are carried out for different ratios of coupling constants characterizing the vector and scalar 4-fermion interaction, $ξ\equiv G_V/G_S$. It is shown that for $ξ< 0.4$ matter is self-bound and for $ξ< 0.65$ it has a first order phase transition of the liquid-gas type. The Gibbs conditions in the mixed phase are applied for the case of two chemical potentials associated with the baryon number and electric charge. The characteristics of the quark stars are calculated for $ξ= 0, 0.5$ and 1. It is found that the phase transition leads to a strong density variation at the surface of these stars. For $ξ= 1$ the properties of quark stars show behaviors typical for neutron stars. At $ξ\goo 0.4$ the stars near to the maximum mass have a large admixture of strange quarks in their interiors.

astro-ph↗

Strange quark matter within the Nambu-Jona-Lasinio model

Equation of state of baryon rich quark matter is studied within the SU(3) Nambu-Jona-Lasinio model with flavour mixing interaction. Possible bound states (strangelets) and chiral phase transitions in this matter are investigated at various values of strangeness fraction S/3B. The model predictions are very sensitive to the ratio of vector (Gv) and scalar (Gs) coupling constants. At Gv/Gs=0.5 and zero temperature the maximum binding energy (about 15 MeV per baryon) takes place when strangeness fraction is about 0.4. Such strangelets are negatively charged and have typical life times of the order of 100 ns. Calculations are carried out also at finite temperatures. They show that bound states exist up to temperatures of about 15 MeV. The model predicts a first order chiral phase transition at finite baryon densities. The parameters of this phase transition are calculated as function of strangeness fraction.

hep-ph↗

Unusual bound states of quark matter within the NJL model

Properties of dense quark matter in and out of chemical equilibrium are studied within the SU(3) Nambu-Jona-Lasinio model. In addition to the 4-fermion scalar and vector terms the model includes also the 6-fermion flavour mixing interaction. First we study a novel form of deconfined matter, meso-matter, which is composed of equal number of quarks and antiquarks. It can be thought of as a strongly compressed meson gas where mesons are melted into their elementary constituents, quarks and antiquarks. Strongly bound states in this quark-antiquark matter are predicted for all flavour combinations of quark-antiquark pairs. The maximum binding energy reaches up to 180 MeV per pair for mixtures with about 70% of strange quark-antiquark pairs. Equilibrated baryon-rich quark matter with various flavour compositions is also studied. In this case only shallow bound states appear in systems with a significant admixture (about 40%) of strange quarks (strangelets). Their binding energies are quite sensitive to the relative strengths of scalar and vector interactions. The common property of all these bound states is that they appear at high particle densities when the chiral symmetry is nearly restored. Thermal properties of meso-matter as well as chemically equilibrated strange quark matter are also investigated. Possible decay modes of these bound states are discussed.

hep-ph↗

Metastable quark-antiquark droplets within the Nambu-Jona-Lasinio model

Chemically non-equilibrated quark-antiquark matter is studied within the Nambu-Jona-Lasinio model. The equations of state of non-strange (q=u,d) and strange (q=s) quark-antiquark systems are calculated in the mean-field approximation. The existence of metastable bound states with zero pressure is predicted at finite densities and temperatures less than about 50 MeV. It is shown that the minimum energy per particle occurs for symmetric systems, with equal densities of quarks and antiquarks. At T=0 these metastable states have quark number densities of about 0.5 fm^-3 for q=u,d and of 1 fm^-3 for q=s. A first order chiral phase transition is found at finite densities and temperatures. The critical temperature for this phase transition is approximately 75 MeV (90 MeV) for the non-strange (strange) baryon-free quark-antiquark matter. For realistic choices of parameters, the model does not predict the phase transition in chemically equilibrated systems. Possible decay channels of the metastable quark-antiquark droplets and their signatures in relativistic heavy-ion collisions are discussed.

hep-ph↗

Collective mechanism of dilepton production in high-energy nuclear collisions

Collective bremsstrahlung of vector meson fields in relativistic nuclear collisions is studied within the time-dependent Walecka model. Mutual deceleration of the colliding nuclei is described by introducing the effective stopping time and average rapidity loss of baryons. It is shown that electromagnetic decays of virtual omega-mesons produced by bremsstrahlung mechanism can provide a substantial contribution to the soft dilepton yield at the SPS bombarding energies. In particular, it may be responsible for the dilepton enhancement observed in 160 AGev central Pb+Au collisions. Suggestions for future experiments to estimate the relative contribution of the collective mechanism are given.

hep-ph↗

Dilepton production by bremsstrahlung of meson fields in nuclear collisions

We study the bremsstrahlung of virtual omega mesons due to the collective deceleration of nuclei at the initial stage of an ultrarelativistic heavy-ion collision. It is shown that electromagnetic decays of these mesons may give an important contribution to the observed yields of dileptons. Mass spectra of positron-electron and muon pairs produced in central Au+Au collisions are calculated under some simplifying assumptions on the space-time variation of the baryonic current in a nuclear collision process. Comparison with the CERES data for 160 AGev Pb+Au collisions shows that the proposed mechanism gives a noticeable fraction of the observed lepton pairs in the intermediate region of invariant masses. Sensitivity of the dilepton yield to the in-medium modification of masses and widths of vector mesons is demonstrated.

hep-ph↗

Particle production by time-dependent meson fields in relativistic heavy-ion collisions

Collective bremsstrahlung of vector meson fields caused by mutual deceleration of the colliding nuclei is considered within the time-dependent Walecka theory. Excitation functions and rapidity distributions of particles produced by this mechanism are calculated under some simplifying assumptions about the space-time variation of the baryon current in a nuclear collision. In the case of central Au+Au collisions the bremsstrahlung mechanism becomes comparable with particle production in incoherent hadron--hadron collisions above the AGS energies.

hep-ph↗