arXiv subjects

K. Redlich

Publications and source records attributed to K. Redlich.

At least 55 records · Page 3Linked to original sources

arXiv2009

The canonical partition function for relativistic hadron gases

Particle production in high-energy collisions is often addressed within the framework of the thermal (statistical) model. We present a method to calculate the canonical partition function for the hadron resonance gas with exact conservation of the baryon number, strangeness, electric charge, charmness and bottomness. We derive an analytical expression for the partition function which is represented as series of Bessel functions. Our results can be used directly to analyze particle production yields in elementary and in heavy ion collisions. We also quantify the importance of quantum statistics in the calculations of the light particle multiplicities in the canonical thermal model of the hadron resonance gas.

hep-ph↗

arXiv2009

Viscosities in the Gluon-Plasma within a Quasiparticle Model

A phenomenological quasiparticle model, featuring dynamically generated self-energies of excitation modes, successfully describes lattice QCD results relevant for the QCD equation of state and related quantities both at zero and non-zero net baryon density. Here, this model is extended to study bulk and shear viscosities of the gluon-plasma within an effective kinetic theory approach. In this way, the compatibility of the employed quasiparticle ansatz with the apparent low viscosities of the strongly coupled deconfined gluonic medium is shown.

hep-ph↗

arXiv2009

Statistical hadronization of heavy flavor quarks in elementary collisions: successes and failures

We analyze recently compiled data on the production of open heavy flavor hadrons and quarkonia in e+e- as well as pp and p-nucleus collisions in terms of the statistical hadronization model. Within this approach the production of open heavy flavor hadrons is well described with parameters deduced from a thermal analysis of light flavor hadron production. In contrast, quarkonium production in such collisions cannot be described in this framework. We point out the relevance of this finding for our understanding of quarkonium production in ultra-relativistic nucleus-nucleus collisions.

hep-ph↗

arXiv2009

Bulk viscosity in quasi particle models

We discuss transport properties of dynamical fluid composed of quasi-particles whose masses depend on temperature and charge chemical potentials. Based on the relativistic kinetic theory formulated under the relaxation time approximation, we derive a general expression for the bulk viscosity in the quasi-particle medium. We show that dynamically generated particle masses imply an essential modification of the fluid compressibility. As an application of our results we consider a class of quasi-particle models with the chiral phase transition belonging to O(4) and Z(2) universality class. Based on the Ginzburg-Landau and the scaling theory we study the critical properties of the bulk viscosity zeta near the phase transition. We show that under the relaxation time approximation the zeta is not expected to show singular behavior near the O(4) and Z(2) critical point through static critical exponents.

hep-ph↗

arXiv2009

Thermal description of hadron production in e+e- collisions revisited

We present a comprehensive analysis of hadron production in e+e- collisions at different center-of-mass energies in the framework of the statistical model of the hadron resonance gas. The model is formulated in the canonical ensemble with exact conservation of all relevant quantum numbers. The parameters of the underlying model were determined using a fit to the average multiplicities of the latest measurements at $\sqrt{s}$ = 10, 29-35, 91 and 130-200 GeV. The results demonstrate that, within the accuracy of the experiments, none of the data sets is satisfactorily described with this approach, calling into question the notion that particle production in e+e- collisions is thermal in origin.

hep-ph↗

arXiv2009

The Functional Renormalization Group and O(4) scaling

The critical behavior of the chiral quark-meson model is studied within the Functional Renormalization Group (FRG). We derive the flow equation for the scale dependent thermodynamic potential at finite temperature and density in the presence of a symmetry-breaking external field. Within this scheme, the critical scaling behavior of the order parameter, its transverse and longitudinal susceptibilities as well as the correlation lengths near the chiral phase transition are computed. We focus on the scaling properties of these observables at non-vanishing external field when approaching the critical point from the symmetric as well as from the broken phase. We confront our numerical results with the Widom-Griffiths form of the magnetic equation of state, obtained by a systematic epsilon-expansion of the scaling function. Our results for the critical exponents are consistent with those recently computed within Lattice Monte-Carlo studies of the O(4) spin system.

hep-ph↗

arXiv2009

Canonical Statistical Model and hadron production in $e^+e^-$ annihilations

We discuss the production of hadrons in $e^+e^-$ collisions at $\sqrt s=91$ GeV. We address the question wether the particle yields measured in the final states are consistent with the statistical model predictions. In the model formulation we account for exact conservation of all relevant quantum numbers using the canonical description of the partition function. Within our model the validity of the thermodynamical approach to quantify particle production in $e^+e^-$ annihilations is not obvious.

hep-ph↗

arXiv2009

Statistical Model Predictions for p+p and Pb+Pb Collisions at LHC

Particle production in p+p and central Pb+Pb collisions at LHC is discussed in the context of the statistical thermal model. For heavy-ion collisions, predictions of various particle ratios are presented. The sensitivity of several ratios on the temperature and the baryon chemical potential is studied in detail, and some of them, which are particularly appropriate to determine the chemical freeze-out point experimentally, are indicated. Considering elementary interactions on the other hand, we focus on strangeness production and its possible suppression. Extrapolating the thermal parameters to LHC energy, we present predictions of the statistical model for particle yields in p+p collisions. We quantify the strangeness suppression by the correlation volume parameter and discuss its influence on particle production. We propose observables that can provide deeper insight into the mechanism of strangeness production and suppression at LHC.

hep-ph↗

arXiv2008

Quarkyonic Matter and Chiral Symmetry Breaking

The appearance of a new phase of QCD, Quarkyonic Matter in the limit of large number of colors is studied within Nambu-Jona-Lassinio effective chiral model coupled to the Polyakov loop. The interplay of this novel QCD phase with chiral symmetry restoration and color deconfinement is discussed. We find that at vanishing temperature and at large $N_c$, the quarkyonic transition occurs at densities only slightly lower than that expected for the chiral transition. This property is also shown to be valid at finite temperature if the temperature is less than that of deconfinement. The position and $N_c$-dependence of chiral critical end point is also discussed.

hep-ph↗

arXiv2008

Transport coefficients near chiral phase transition

We analyze the transport properties of relativistic fluid composed of constituent quarks at finite temperature and density. We focus on the shear and bulk viscosities and study their behavior near chiral phase transition. We model the constituent quark interactions through the Nambu--Jona Lasinio Lagrangian. The transport coefficients are calculated within kinetic theory under relaxation time approximation including in--medium modification of quasi--particles dispersion relations. We quantify the influence of the order of chiral phase transition and the critical end point on dissipative phenomena in such a medium. Considering the changes of shear and bulk viscosities along the phase boundary we discuss their sensitivity to probe the existence of the critical end point.

hep-ph↗

arXiv2008

Kurtosis and compressibility near the chiral phase transition

The properties of net quark number fluctuations in the vicinity of the QCD chiral phase transition are discussed in terms of an effective chiral model in the mean-field approximation. We focus on the ratio of the fourth- to second- order cumulants (kurtosis) and the compressibility of the system and discuss their dependence on the pion mass. It is shown that near the chiral phase transition, both observables are sensitive to the value of $m_π$. For physical $m_π$, the kurtosis exhibits a peak whereas the inverse compressibility shows a dip at the pseudocritical temperature. These structures disappear for large $m_π$. Our results, obtained in an effective model with two flavors, are qualitatively consistent with recent results of 2+1 flavor lattice gauge theory. We also discuss the high- and low-temperature properties of these observables and the role of the coupling of the quark degrees of freedom to the Polyakov loop.

hep-ph↗

arXiv2008

Particle production in p-p collisions and prediction for LHC energy

We analyze recent data on particle production yields obtained in p-p collisions at SPS and RHIC energies within the statistical model. We apply the model formulated in the canonical ensemble and focus on strange particle production. We introduce different methods to account for strangeness suppression effects and discuss their phenomenological verification. We show that at RHIC the midrapidity data on strange and multistrange particle multiplicity can be successfully described by the canonical statistical model with and without an extra suppression effects. On the other hand, SPS data integrated over the full phase-space require an additional strangeness suppression factor that is beyond the conventional canonical model. This factor is quantified by the strangeness saturation parameter or strangeness correlation volume. Extrapolating all relevant thermal parameters from SPS and RHIC to LHC energy we present predictions of the statistical model for particle yields in p-p collisions at sqrt(s) = 14TeV. We discuss the role and the influence of a strangeness correlation volume on particle production in p-p collisions at LHC.

hep-ph↗

arXiv2008

The Phase Diagram of Hadronic Matter

We interpret the phase structure of hadronic matter in terms of the basic dynamical and geometrical features of hadrons. Increasing the density of constituents of finite spatial extension, by increasing the temperature T or the baryochemical potential mu, eventually "fills the box" and eliminates the physical vacuum. We determine the corresponding transition as function of T and mu through percolation theory. At low baryon density, this means a fusion of overlapping mesonic bags to one large bag, while at high baryon density, hard core repulsion restricts the spatial mobility of baryons. As a consequence, there are two distinct limiting regimes for hadronic matter. We compare our results to those from effective chiral model studies.

hep-ph↗

arXiv2008

Statistical hadronization of charm: from FAIR to the LHC

We discuss the production of charmonium in nuclear collisions within the framework of the statistical hadronization model. We demonstrate that the model reproduces very well the availble data at RHIC. We provide predictions for the LHC energy where, dependently on the charm production cross section, a dramatically different behaviour of charmonium production as a function of centrality might be expected. We extend our predictions for charm production towards the threshold energies, where charm is expected to be measured at the future FAIR facility.

nucl-th↗

arXiv2008

Density Fluctuations as Signature of a Non--Equilibrium First Order Phase Transition

We show that in the presence of spinodal instabilities which develop at a first order phase transition, the fluctuations of conserved charges can be as strong as those at the critical end point (CEP). In particular, the net baryon number susceptibility diverges as the system crosses the isothermal spinodal lines. This indicates that charge density fluctuations can be used not only to probe the CEP but also the non--equilibrium first order chiral phase transition in heavy ion collisions.

hep-ph↗

arXiv2008

Density fluctuations and a first-order chiral phase transition in non-equilibrium

The thermodynamics of a first-order chiral phase transition is considered in the presence of spinodal phase separation using the Nambu-Jona-Lasinio model in the mean field approximation. We focus on the behavior of conserved charge fluctuations. We show that in non-equilibrium the specific heat and charge susceptibilities diverge as the system crosses the isothermal spinodal lines.

hep-ph↗

arXiv2007

Density fluctuations and chiral phase transition

Based on an effective QCD Lagrangian we discuss the properties of charge density fluctuations in the vicinity of chiral phase transition. We explore thermodynamics in the presence of spinodal phase separation. We show that appearance of spinodal decomposition in a non-equilibrium first order phase transition results in divergence of the charge density fluctuations related with the electric charge and baryon number conservation. Consequently, divergent fluctuations at the chiral phase transition are not only attributed to the critical end point but are also there along the first order phase transition if the spinodal phase separation take place. Based on the mean field dynamics, the critical exponents for these singular behavior of charge susceptibilities are also discussed.

hep-ph↗

arXiv2007

Chiral phase transition in the presence of spinodal decomposition

The thermodynamics of a first order chiral phase transition is considered in the presence of spinodal phase separation within the Nambu-Jona-Lasinio (NJL) model. The properties of the basic thermodynamic observables in the coexistence phase are discussed for zero and non-zero quark masses. We focus on observables that probe the chiral phase transition. In particular, the behavior of the specific heat and entropy as well as charge fluctuations are calculated and analyzed. We show that the specific heat and charge susceptibilities diverge at the isothermal spinodal lines. We determine the scaling behavior and compute the critical exponent $γ$ of the net quark number susceptibility at the isothermal spinodal lines within the NJL model and the Ginsburg-Landau theory. We show that in the chiral limit the critical exponent $γ=1/2$ at the tricritical point as well as along the isothermal spinodal lines. On the other hand, for finite quark masses the critical exponent at the spinodal lines, $γ=1/2$, differs from that at the critical end point, $γ=2/3$, indicating a change in the universality class. These results are independent of the particular choice of the chiral Lagrangian and should be common for all mean field approaches.

hep-ph↗