arXiv subjects

K. Redlich

Publications and source records attributed to K. Redlich.

At least 109 records · Page 6Linked to original sources

arXiv2003

Statistical hadronization of charm in heavy-ion collisions at SPS, RHIC and LHC

We study the production of charmonia and charmed hadrons in nucleus-nucleus collisions at SPS, RHIC, and LHC energies within the framework of the statistical hadronization model. Results from this model are compared to the measured yields and centrality dependence of J/psi production at SPS and RHIC energies. We explore and contrast the centrality dependence of the production of mesons with open and hidden charm at SPS, RHIC, and LHC. The sensitivity of the results to various input parameters is analyzed in detail for RHIC energy.

nucl-th↗

arXiv2003

Thermodynamics at Non-Zero Baryon Number Density: A Comparison of Lattice and Hadron Resonance Gas Model Calculations

We compare recent lattice studies of QCD thermodynamics at non-zero quark chemical potential with the thermodynamics of a hadron resonance gas. We argue that for T < Tc the equation of state derived from Monte--Carlo simulations of two flavour QCD at non-zero chemical potential can be well described by a hadron resonance gas when using the same set of approximations as used in current lattice calculations. We estimate the importance of truncation errors arising from the use of a Taylor expansion in terms of the quark chemical potential and examine the influence of unphysically large quark masses on the equation of state and the critical conditions for deconfinement.

hep-ph↗

arXiv2003

Particle Production in Heavy Ion Collisions

The status of thermal model descriptions of particle production in heavy ion collisions is presented. We discuss the formulation of statistical models with different implementation of the conservation laws and indicate their applicability in heavy ion and elementary particle collisions. We analyze experimental data on hadronic abundances obtained in ultrarelativistic heavy ion collisions, in a very broad energy range starting from RHIC/BNL ($\sqrt s=200$ A GeV), SPS/CERN ($\sqrt s\simeq 20$ A GeV) up to AGS/BNL ($\sqrt s\simeq 5$ A GeV) and SIS/GSI ($\sqrt s\simeq 2$ A GeV) to test equilibration of the fireball created in the collision. We argue that the statistical approach provides a very satisfactory description of experimental data covering this wide energy range. Any deviations of the model predictions from the data are indicated. We discuss the unified description of particle chemical freeze--out and the excitation functions of different particle species. At SPS and RHIC energy the relation of freeze--out parameters with the QCD phase boundary is analyzed. Furthermore, the application of the extended statistical model to quantitative understanding of open and hidden charm hadron yields is considered.

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arXiv2003

Hadron Resonance Mass Spectrum and Lattice QCD Thermodynamics

We confront lattice QCD results on the transition from the hadronic phase to the quark--gluon plasma with hadron resonance gas and percolation models. We argue that for T < T_c the equation of state derived from Monte--Carlo simulations of (2+1) quark--flavor QCD can be well described by a hadron resonance gas. We examine the quark mass dependence of the hadron spectrum on the lattice and discuss its description in terms of the MIT bag model. This is used to formulate a resonance gas model for arbitrary quark masses which can be compared to lattice calculations. We finally apply this model to analyze the quark mass dependence of the critical temperature obtained in lattice calculations. We show that the value of T_c for different quark masses agrees with lines of constant energy density in a hadron resonance gas. For large quark masses a corresponding contribution from a glueball resonance gas is required.

hep-ph↗

arXiv2003

Group projection method in statistical systems

We discuss an application of group theoretical methods to the formulation of the thermodynamics of systems constrained by the conservation laws described by a semi--simple compact Lie group. A general projection method that allows to construct a partition function for a given irreducible representation of the Lie group is outlined. Applications of the method in Lattice Gauge Theory (LGT) for non--zero baryon number and in the phenomenological description of particle production in ultrarelativistic heavy ion collisions are also indicated.

hep-ph↗

arXiv2002

Statistical hadronization of charm at SPS, RHIC and LHC

We study the production of charmonia and charmed hadrons for nucleus-nucleus collisions at SPS, RHIC, and LHC energies within the framework of the statistical hadronization model. Results from this model are compared to the observed centrality dependence of J/psi production at SPS energy. We further provide predictions for the centrality dependence of the production of open and hidden charm mesons at RHIC and LHC.

nucl-th↗

arXiv2002

From the Dyson-Schwinger to the Transport Equation in the Background Field Gauge of QCD

The non-equilibrium quantum field dynamics is usually described in the closed-time-path formalism. The initial state correlations are introduced into the generating functional by non-local source terms. We propose a functional approach to the Dyson-Schwinger equation, which treats the non-local and local source terms in the same way. In this approach, the generating functional is formulated for the connected Green functions and one-particle-irreducible vertices. The great advantages of our approach over the widely used two-particle-irreducible method are that it is much simpler and that it is easy to implement the procedure in a computer program to automatically generate the Feynman diagrams for a given process. The method is then applied to a pure gluon plasma to derive the gauge-covariant transport equation from the Dyson-Schwinger equation in the background covariant gauge. We discuss the structure of the kinetic equation and show its relationship with the classical one. We derive the gauge-covariant collision part and present an approximation in the vicinity of equilibrium. The role of the non-local source kernel in the non-equilibrium system is discussed in the context of a free scalar field.

hep-ph↗

arXiv2002

Probing Hadronization with Strangeness

The Omega-bar/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interaction at SPS energies. The anti-omega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.

nucl-th↗

arXiv2002

Kinetic Equation for Gluons in the Background Gauge of QCD

We derive the quantum kinetic equation for a pure gluon plasma, applying the background field and closed-time-path method. The derivation is more general and transparent than earlier works. A term in the equation is found which, as in the classical case, corresponds to the color charge precession for partons moving in the gauge field.

nucl-th↗

arXiv2001

Strange Particle Production from SIS to LHC

>1A review of meson emission in heavy ion collisions at incident energies from SIS up to collider energies is presented. A statistical model assuming chemical equilibrium and local strangeness conservation (i.e. strangeness conservation per collision) explains most of the observed features. Emphasis is put onto the study of $K^+$ and $K^-$ emission at low incident energies. In the framework of this statistical model it is shown that the experimentally observed equality of $K^+$ and $K^-$ rates at ``threshold-corrected'' energies $\sqrt{s} - \sqrt{s_{th}}$ is due to a crossing of two excitation functions. Furthermore, the independence of the $K^+$ to $K^-$ ratio on the number of participating nucleons observed between SIS and RHIC is consistent with this model. It is demonstrated that the $K^-$ production at SIS energies occurs predominantly via strangeness exchange and this channel is approaching chemical equilibrium. The observed maximum in the $K^+/π^+$ excitation function is also seen in the ratio of strange to non-strange particle production. The appearance of this maximum around 30 $A\cdot$GeV is due to the energy dependence of the chemical freeze-out parameters $T$ and $μ_B$.

nucl-ex↗

arXiv2001

The Statistical Model of Hadrogenesis in A--A collisions from AGS to SPS and RHIC

We discuss experimental data on particle yields and particle spectra obtained in heavy ion collisions in a very broad energy range from SIS/GSI through AGS/BNL up to SPS/CERN and RHIC/BNL. We argue that in this broad energy range hadronic yields and their ratios resemble a thermal equilibrium population along a unified freeze--out curve determined by the condition of fixed energy/particle = 1 GeV. At RHIC and top SPS, thermal parameters are consistent within error with the critical conditions required for deconfinement. This, together with the particular distribution of strangeness within a collision fireball, could indicate that chemical equilibrium is a direct consequence of parton to hadron transition, which populates a state of maximum entropy. At lower energies equilibration in A--A collisions should appear through hadronic interactions and rescatterings.

hep-ph↗

arXiv2001

Strangeness enhancement and Energy dependence in Heavy Ion Collisions

The canonical statistical model analysis of strange and multistrange hadron production in central A-A relative to p-p/p-A collisions is presented over the energy range from $\sqrt s=8.73$ GeV up to $\sqrt s =130$ GeV. It is shown that the relative enhancement of strange particle yields from p-p/p-A to A-A collisions substantially increases with decreasing collision energy. It is largest at $\sqrt s= 8.7$ GeV, where the enhancement of $Ω,Ξ$ and $Λ$ is of the order of 100, 20 and 3, respectively. In terms of the model these results are due to the canonical suppression of particle thermal phase space at lower energies, which increases with the strangeness content of the particle and with decreasing size of the collision fireball. The comparison of the model with existing data on energy dependence of the kaon/pion ratio is also discussed.

hep-ph↗

arXiv2001

Chemical equilibration of U(1) charged particles in a thermal environment

We discuss chemical equilibration of particles carrying non-vanishing quantum numbers related with U(1) internal symmetry. We construct the transport equation for the time evolution of particle multiplicities and their probability functions. The solution of these equations is obtained in different limiting cases. It is argued that a U(1) charged particles, dependent on thermal conditions inside a fireball, approaches different equilibrium limits. The differences between kinetics of abundantly and rarely produced particles are explained.

hep-ph↗

arXiv2001

Conservation Laws and Particle Production in Heavy Ion Collisions

We discuss the role of the conservation laws related with U(1) internal symmetry group in the statistical model description of particle productions in ultrarelativistic heavy ion collisions. We derive and show the differences in particle multiplicities in the canonical and the grand canonical formulation of quantum number conservation. The time evolution and the approach to chemical equilibrium in the above ensembles is discussed in terms of kinetic master equation. The application of the statistical model to the description of (multi)strange particle yields at GSI/SIS and the SPS energies is also presented.

hep-ph↗

arXiv2001

Overpopulation of $\bar Ω$ in pp collisions: a way to distinguish statistical hadronization from string dynamics

The $\barΩ/Ω$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\rm lab}$=160 GeV). The anti-omega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.

hep-ph↗

arXiv2001

Hadron production in Au-Au collisions at RHIC

We present an analysis of particle production yields measured in central Au-Au collisions at RHIC in the framework of the statistical thermal model. We demonstrate that the model extrapolated from previous analyses at SPS and AGS energy is in good agreement with the available experimental data at $\sqrt s=130$ GeV implying a high degree of chemical equilibration. Performing a $χ^2$ fit to the data, the range of thermal parameters at chemical freezeout is determined. At present, the best agreement of the model and the data is obtained with the baryon chemical potential $μ_B\simeq 46\pm 5$ MeV and temperature $T\simeq 174\pm 7$ MeV. More ratios, such as multistrange baryon to meson, would be required to further constrain the chemical freezeout conditions. Extrapolating thermal parameters to higher energy, the predictions of the model for particle production in Au-Au reactions at $\sqrt s=200$ GeV are also given.

hep-ph↗

arXiv2001

Maximum Relative Strangeness Content in Heavy Ion Collisions Around 30 A.GeV

It is shown that the ratio of strange to non-strange particle production in relativistic heavy ion collisions is expected to reach a maximum at beam energies around 30 A.GeV in the lab frame. This maximum is unique to heavy ion collisions, and has no equivalent in elementary particle collisions. The appearance of the maximum is due to the energy dependence of the chemical freeze-out parameters and is clearly seen as a pronounced peak in the Wroblewski factor as a function of the incident energy as well as in the behavior of the K+/pi+ ratio. Below 30 A.GeV strange baryons contribute strongly because of the very large value of the chemical potential muB. As the energy increases, the decrease of the baryon chemical potential coupled with only moderate increases in the associated temperature causes a decline in the relative number of strange baryons above energies of about 30 A.GeV leading to very pronounced maxima in the Lambda/pi+ and Xi-/pi+ ratios.

hep-ph↗

arXiv2001

Strangeness enhancement in heavy ion collisions

We argue that the main features of baryon and anti-baryon enhancement observed by the WA97 collaboration can be described using canonical formulation of strangeness conservation. Within this formulation strangeness enhancement could be larger at lower collision energies.

hep-ph↗