The Nonlinear Eigenfrequency Shift in QGP

The kinetic equations for quark-gluon plasma (QGP) are studied beyond the linear response theory, and the nonlinear eigenfrequency shift owing to the non-Abelian interaction of the color eigenmodes in a spatially uniform QGP is calculated.     

Alternating chaotic and periodic dynamics in Chern-Simons-Higgs theory with scalar magnetic interaction

The dynamical behavior of a Chern-Simons-Higgs system is studied for the spatially homogeneous case. The model, described by interacting gauge and scalar fields includes two parity and time violating terms: the Chern-Simons and the scalar magnetic interaction. For the pure Chern-Simons part of the theory the equations of motion are integrable. In general, however, the model system exhibits an interesting pattern of chaos to order transitions as the scalar magnetic moment is varied. The system dynamics are analyzed using a combination of standard techniques, such as phase space portraits, Lyapunov exponents, and Fourier spectra. (c) 2000 American Institute of Physics.     

Transport coefficients of quark-gluon plasma

Transport coefficients of quark-gluon plasma are discussed in the framework of relativistic kinetic theory with the relaxation time approximation of Boltzmann transport equation. The expressions for the coefficients of shear and volume viscosities and heat conductivity are derived assuming quark-gluon plasma to be a non-reactive mixture of quarks, anti-quarks and gluons. A lowest order in deviations from local thermal equilibrium and in plasma phase, lowest order in coupling constant are assumed. Entropy production due to irreversible processes is discussed.     

Strangeness production in quark-gluon plasma

In this paper it is shown that the strangeness production in quark-gluon plasma might not serve as an experimental signature for the formation of quark-gluon plasma. Our results are completely based on the computer simulation of the plasma. We have taken into account the full three-dimensional hydrodynamic expansion of the plasma.     

Hadrons yielded by plasma

We consider nonequilibrium phase transitions of a quark-gluon plasma into hadrons proceeding via deflagration and supersonic condensation. The possible existence of a third phase, i.e. plasma of constitutent quarks is taken into account. New equations of state for hadronic gas are used, which include the proper volume of particles in a thermodynamically consistent way. The yields of hadrons are calculated for various values of the baryon density of the quark-gluon plasma.     

Transport coefficients of QCD matter

Transport coefficients of QCD matter are discussed in the framework of relativistic kinetic theory. Expressions for shear and bulk viscosities and heat conductivity are derived in lowest order in deviations from local thermal equilibrium. Pure gluon matter is considered both at low temperatures in the glueball phase and at high temperatures in the gluon plasma phase, and quark-gluon matter is considered in the high-temperature plasma phase. In the critical region nonperturbative calculations based on Kubo formulas should be attempted. Applications to ultra-relativistic nucleus-nucleus collisions are discussed.     

Phase transitions of a quark-gluon plasma to hadrons

We have studied phase transitions of a quark-gluon plasma to hadrons, which occur by detonation, deflagration, supersonic condensation and evaporation. Consideration is given to the spectra of the yields of various hadrons which are produced in each of these transitions. The process of expansion and overcooling of a quark-gluon plasma is simulated.     

Zero-Density Phase Transition to Quark-Gluon Plasma and the Relativistic Finite Baryon Volume Effect in Hadronic Matter

We examine the role of relativistic finite baryon volume effect in the phase transition between hadronic matter and quark-gluon plasma at vanishing baryon density. It is found that the appearance of abnormal state at high temperature may enhance the baryon-antibaryon excitation, which has large influence on the quark-gluon plasma formation. The numerical results show that the occurence of this phase transition depends on how to extrapolate the nucleon-scalar meson coupling constant to the baryonic resonance-scalar meson coupling.     

Effect of long-range correlation on scaling behavior of normalized factorial moments for the first-order phase transition

Within the framework of Ginzburg–Landau theory, the effect of multiplicity correlation between the dynamical multiplicity fluctuations is analyzed for a first-order phase transition from quark–gluon plasma to hadrons.Normalized factorial correlators are used to study the correlated dynamical fluctuations. A scaling behavior is found among the factorial correlators, and an approximate universal exponent, which is weakly dependent on the details of the phase transition, is obtained.     

Phase transitions in nuclear matter: metastability and fluctuations

Supercooled and overheated metastable states near the phase transition between hadronic matter and the quark-gluon plasma are considered. The Blaizot-Ollitraut equation of state is generalized to include metastable states. A stability criterion is formulated and its connection with the Ginzburg parameter, familiar in the theory of phase transitions, is established. Fluctuations and bubble creation as well as an inflation scenario of the universe during its hadronic era are discussed.     

In-medium effects on charmonium production in heavy-ion collisions

Charmonium production in heavy-ion collisions is investigated within a kinetic theory framework incorporating in-medium properties of open- and hidden-charm states in line with recent QCD lattice calculations. A continuously decreasing open-charm threshold across the phase boundary of hadronic and quark-gluon matter is found to have important implications for the equilibrium abundance of charmonium states. The survival of J/psi resonance states above the transition temperature enables their recreation also in the quark-gluon plasma. Including effects of chemical and thermal off-equilibrium, we compare our model results to available experimental data at CERN SPS and BNL RHIC energies. In particular, earlier found discrepancies in the psi(')/psi ratio can be resolved.     

Low mass dielectrons at LHC energy

We study the thermal production of low mass dielectrons in central nucleus-nucleus collisions at LHC energy. We assume initial quark-gluon plasma production, followed by a first order quark-hadron phase transition and subsequent hadronization; the expansion of the system is described by Bjorken's hydrodynamical model. In the quark-gluon plasma, we include both the basisq annihilation process and lowest order QED and QCD corrections. In the hadronic phase, we consider pion annihilation as well as pion scattering with virtual bremsstrahlung leading to dielectron production. Our results are then compared to dielectron rates from ⁰ and Dalitz decays. We conclude that it will be rather difficult to disentangle the quark-gluon plasma contributions from competing dielectron production processes.     

Quark-gluon plasma diagnostics in a successive equilibrium scenario

The relativistic Fokker-Planck equation has been used to study the evolution of the quark distribution in the quark-gluon phase expected to be formed in ultra-relativistic heavy-ion collisions. The effect of thermal masses for quarks and gluons is incorporated to take account of the in-medium properties. We find that the kinetic equilibrium is achieved before the system reaches the critical temperature of quark-hadron phase transition. We find that chemical equilibrium is not achieved during this time. We have evaluated the electromagnetic probes of quark-gluon plasma from the non-equilibrated quark-gluon phase and compared them with those in completely equilibrated scenario. The hard QCD production rates for the electromagnetic ejectiles as well as the heavy quark production rates are also calculated.     

On the photon production in nucleus-nucleus collisions at high energy

A modified Landau hydrodynamical model is applied to study hard thermal photon production in central heavy-ion collisions at LHC, RHIC and SPS energies. It is shown that the phase transition from quark-gluon plasma into hadrons in consequence of the thermodynamical expansion is close to the second order phase transition if a resonance production is taken into account. Hard direct photon emission is also investigated with consideration of nuclear shadowing effect on structure function of quarks and gluons. Also π^π photon background is investigated. It is demonstrated that at the LHC energy photon yield from the quark-gluon plasma in the photon transversal momentumk _⊥ range from 5 to 25 GeV/c exceeds both the background and the direct photon yield. This conclusion may be important for the quark-gluon plasma diagnostic aims. It is also shown that for the LHC energy the thermal photon yield in the present model essentially exceeds this yield obtained in the Bjorken scaling model.     

Anomalous viscosity of an expanding quark-gluon plasma

We argue that an expanding quark-gluon plasma has an anomalous viscosity, which arises from interactions with dynamically generated color fields. We derive an expression for the anomalous viscosity in the turbulent plasma domain and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma is near equilibrium. The anomalous viscosity dominates over the collisional viscosity for weak coupling and not too late times. This effect may provide an explanation for the apparent "nearly perfect" liquidity of the matter produced in nuclear collisions at the Relativistic Heavy Ion Collider without the assumption that it is a strongly coupled state.     

QCD at finite temperature

Quantum chromodynamics is studied at finite temperatures and densities using the temperature Green functions method. For the Green functions the renormalized Schwinger-Dyson equations are obtained and their qualitative properties are discussed. The equality of the renormalization constants for the equations obtained at T, μ ≠ 0 with those for quantum field theory is pointed out. General properties of the gluon polarization tensor are investigated at T, μ ≠ 0. The temperature Green functions are calculated within the one-loop approximation using both relativistic and axial gauges. The fulfilment of the Slavnov-Taylor identities is verified. The asymptotic behaviour of the polarization tensor at T, μ ≠ 0 is established and the excitation spectrum of quark-gluon plasma is found. Both Fermi and Bose excitations are considered and the gauge invariance of the spectra is demonstrated. The renormalization group extension of the dispersion laws into the regions of high temperatures and densities is presented. The exact representation of the thermodynamical potential in QCD is found in terms of the temperature Green functions. For the quark-gluon plasma the thermodynamical potential is calculated with the g³-term taken into account. The equation of state of the hot quark-gluon plasma is found and its properties are discussed. The complete evolutional diagram of the hadronic matter is outlined. The phase curve asymptotics, which put bounds on the quark-gluon plasma domain, are found for the two limiting cases (μ = 0, T → T₀; T = 0, μ → μ₀). The phase transition of the hot quark-gluon plasma placed in external Abelian field is studied. The instability of such plasma has been found and the program of its stabilization is indicated. The infrared behaviour of the non-Abelian gauge theory is studied for finite temperatures when power divergencies are essential. The propagator of transverse gluons is shown to be singular for momenta |p| ˜ g²T and this cannot be avoided by summing the simplest bubble chains. The infrared asymptotic behaviour of the tree-gluon vertex is found and the results obtained are checked using the Slavnov-Taylor identities. The Green functions asymptotics found indicate either an instability of the quark-gluon plasma in the infrared momentum domain or the inconsistency of the perturbational methods. A non-perturbative approach to the infrared problem in QCD is developed within the axial gauge. The closed equations for the structure functions that determine the gluon polarization tensor are obtained by using the Slavnov-Taylor identities to found approximately the three-gluon vertex. It is shown that the solution of the equations obtained by iterations does not remove the infrared singularity from the temperature Green functions. The nonperturbative solution of such equations is discussed.     

Dynamics of the hadronization phase transition at finite baryon chemical potentials

The dynamics of the expansion (conserving total baryon number and entropy) of a quark-gluon plasma which undergoes a first-order phase transition into a hadron resonance gas is studied. An increase of the temperature and a long lifetime of the system are observed in the two-phase coexistence region. These phenomena may prove to be crucial for the survival of strongly interacting probes which have been proposed as signals for the formation of a quark-gluon plasma.     

Two-photon correlations as the signal of a sharp transition in quark-gluon plasma

The photon production arising due to time variation of a medium has been considered. The Hamilton formalism for photons in a time-variable medium (plasma) has been developed with application to inclusive photon production. The results have been used for calculation of the photon production in the course of the transition from a quark-gluon phase to a hadronic phase in relativistic heavy-ion collisions. The relative strength of the effect and the specific two-photon correlations have been evaluated. It is demonstrated that the opposite-side two-photon correlations are indicative of a sharp transition from the quark-gluon phase to hadrons.     

Constraints for critical temperature of the phase transition into the quark-gluon plasma

Low temperature of the phase transition into the quark-gluon plasma correspond to low values of the bag model constant and to absolutely stable strange quark matter. Some of the observed pulsars are identified quite reliably as neutron stars. If strange matter is stable, the central density of these pulsars is to be smaller that critical density of the phase transition into the nonstrange quark matter. The nonstrange quark matter being formed turns to more stable strange matter on a weak interaction timescale converting neutron stars into strange stars. The requirement of stability of old and newly born neutron stars is used to constrain the bag model constant and the critical temperature of the phase transition into the quark-gluon plasma at zero chemical potential.