Strangeness changing processes in hadronization and elastic scattering for a chirally invariant transport theory

Transition rates for strangeness changing processes due to hadronization of two mesons from a quark and antiquark, $q\bar q \to MM'$ , are studied as a function of temperature in the SU (3) Nambu-Jona-Lasinio model. It is found that this process accounts for maximally 15% of the increase of the observed excess in theK/π ratio atT=150 MeV. Elastic scattering processes in the plasma, when regarded as solely responsible for the strangeness excess, place an upper limit of 4 fm/c on the plasma lifetime.     

Confining but chirally symmetric dense and cold matter

The possibility for existence of cold, dense chirally symmetric matter with confinement is reviewed. The answer to this question crucially depends on the mechanism of mass generation in QCD and interconnection of confinement and chiral symmetry breaking. This question can be clarified from spectroscopy of hadrons and their axial properties. Almost systematical parity doubling of highly excited hadrons suggests that their mass is not related to chiral symmetry breaking in the vacuum and is approximately chirally symmetric. Then there is a possibility for existence of confining but chirally symmetric matter. We clarify a possible mechanism underlying such a phase at low temperatures and large density. Namely, at large density the Pauli blocking prevents the gap equation to generate a solution with broken chiral symmetry. However, the chirally symmetric part of the quark Green function as well as all color non-singlet quantities are still infrared divergent, meaning that the system is with confinement. A possible phase transition to such a matter is most probably of the first order. This is because there are no chiral partners to the lowest lying hadrons.     

Nuclear mean field from chirally symmetric effective theory

The mean-field theory of the nuclear many-body problem proposed recently by Furnstahl, Serot, and Tang (FST) is discussed. The FST chiral Lagrangian is derived in terms of an effective field theory. This new approach allows one to construct in a controlled manner the universal nuclear Lagrangian consistent with symmetries of QCD. The FST Lagrangian is constructed by using power counting, i.e., the expansion in powers of the lowest lying hadronic fields and their derivatives. Terms in the Lagrangian are organized by applying Georgi’s naive dimensional analysis and “naturalness” condition. The relevant degrees of freedom are nucleons, pions, an isoscalar-vector field ω meson), an isoscalar-scalar field (σ meson), and an isovector-vector field (ρ meson). The chiral symmetry is realized nonlinearly using a standard WCCWZ procedure.     

Shock stability criterion in relativistic hydrodynamics and quark-gluon plasma hadronization

The shock stability condition in the relativistic hydrodynamics is found. This criterion is applied to a quark-gluon plasma shock-like hadronization transition.     

Strange solitons in a chiral quark-meson model

We consider aSU(3) quark soliton model based on chiral invariant quark-meson coupling. We find soliton solutions with nonzero strangeness andB=1 in the model with nontrivial kaonic fields, for values of the coupling constant greater than the phenomenologically acceptable number. Hence they do not correspond to known strange baryons.     

Geometric interpretation of a new hadronization model

It is shown that the phenomenological potential, used in the context of a recent successful hadronization scheme to realize an effective quark confinement, can be reproduced by coupling, to first order, the quark field to the geometry of an anti-de Sitter vacuum. This seems to suggest a geometric interpretation whith could explain and justify the manifest Lorentz noninvariance of the original effective hadronization model.     

The effect of hadronization on the instabilities in an expanding parton plasma

The growth rate for instabilities in an expanding parton plasma is investigated by using a quasiparticle transport model including hadronization. The coupled Boltzmann equations for partons and pions with time dependent mean field masses and source terms are solved in the Bjorken boost invariant picture. Hadronization modifies the known instability in the parton plasma created by the mean field in two ways: In the beginning, hadronization increases the rate Γ of instability, but then Γ→ 0 when the hadronization is dominating the time evolution. Received: 11 January 1999     

Radiation transport in a spherically symmetric hot plasma

An analytical solution is obtained for the problem of radiation transport in a spherically symmetric plasma. The ions are assumed to be in a complete steady state with constant ion density and electron temperature. The radiation density is assumed to be small so that the rate of the radiative processes in the plasma is small relative to that of the collisional processes, but not negligible. The effect of the plasma on the radiation density, as well as the influence of the radiation on the population probabilities, are properly accounted for. Under these conditions explicit expressions are given, valid to the first order in the plasma dimensions, for the radiation density and the population probability of the ionic states.     

Space-time evolution of hadronization

Beside its intrinsic interest for the insights it can give into color confinement, knowledge of the space-time evolution of hadronization is very important for correctly interpreting jet-quenching data in heavy-ion collisions and extracting the properties of the produced medium. On the experimental side, the cleanest environment to study the space-time evolution of hadronization is semi-inclusive deeply inelastic scattering on nuclear targets. On the theoretical side, two frameworks are presently competing to explain the observed attenuation of hadron production: quark energy loss (with hadron formation outside the nucleus) and nuclear absorption (with hadronization starting inside the nucleus). I will discuss recent observables and ideas which will help to distinguish these two mechanisms and to measure the time scales of the hadronization process. PACS 25.30.-c; 25.75.-q; 24.85.+p; 13.87.Fh     

Rapid hadronization and strangeness production

A fast hadronization scenario is presented where a central role is played by the chiral symmetry break-down in the expanding Quark-Gluon Plasma. This mechanism can become effective when thermal damping ceases after the thermal freeze-out of the quark system. We estimate time scales and spatial characteristics of chiral-symmetry breaking instabilities on the basis of an effective field-theoretical model. It is argued that this fast process provides a basis to understand the measured large abundances of strange antibaryons in heavy ion collisions.     

Nonextensive boltzmann equation and hadronization

We present a novel nonextensive generalization of the Boltzmann equation. We investigate the evolution of the one-particle distribution in this framework. The stationary solution is exponential in a nonlinear function of the original energy. The total energy is composed using a general, associative nonextensive rule. We propose that for describing the hadronization of quark matter such rules may apply.