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P. Levai

Publications and source records attributed to P. Levai.

72 records · Page 4Linked to original sources
arXiv2000

Strange mesons from quark and hadron matter: a comparison

In a simplified model we study the hadronization of quark matter in an expanding fireball, in particular the approach to a final hadronic composition in equilibrium. Ideal hadron gas equilibrium constrained by conservation laws, the fugacity parametrization, as well as linear and non-linear coalescence approaches are recognized as different approximations to this in-medium quark fusion process. It is shown that color confinement requires a dependence of the hadronization cross section on quark density in the presence of flow (dynamical confinement).

hep-ph↗
arXiv2000

Simple predictions from ALCOR_c for rehadronisation of charmed quark matter

We study the production of charmed hadrons with the help of ALCOR_c, the algebraic coalescence model for rehadronisation of charmed quark matter. Mesonic ratios are introduced as factors connecting various antibaryon to baryon ratios. The resulting simple relations could serve as tests of quark matter formation and coalescence type rehadronization in heavy ion collisions.

hep-ph↗
arXiv2000

Reaction Operator Approach to Non-Abelian Energy Loss

A systematic expansion of the induced inclusive gluon radiation associated with jet production in a dense QCD plasma is derived using a reaction operator formalism. Analytic expressions for the transverse momentum and light-cone momentum distributions are derived to all orders in powers of the gluon opacity of the medium, $Nσ_g/A=L/λ_g$. The reaction operator approach also leads to a simple algebraic proof of the ``color triviality'' of single inclusive distributions and to a solvable set of recursion relations. The analytic solution generalizes previous continuum solutions (BDMPS) for applications to mesoscopic QCD plasmas. The solution is furthermore not restricted to uncorrelated geometries and allows for evolving screening scales as well as the inclusion of finite kinematic constraints. The later is particularly important because below LHC energies the kinematic constraints significantly decrease the non-abelian energy loss. Our solution for the inclusive distribution also generalizes the finite order exclusive (tagged) distribution case studied previously (GLV1). The form of the analytic solution is well suited for numerical implementation in Monte Carlo event generators to enable more accurate calculations of jet quenching in ultra-relativistic nuclear collisions. Numerical results illustrating the constributions of the first three orders in opacity are compared to the ``self-quenching'' hard radiation intensity. A surprising result is that the induced gluon radiation intensity is dominated by the (quadratic in $L$) first order opacity contribution for realistic geometries and jet energies in nuclear collisions.

nucl-th↗
arXiv2000

Non-Abelian Energy Loss at Finite Opacity

A systematic expansion in opacity, $L/λ$, is used to clarify the non-linear behavior of induced gluon radiation in quark-gluon plasmas. The inclusive differential gluon distribution is calculated up to second order in opacity and compared to the zeroth order (factorization) limit. The opacity expansion makes it possible to take finite kinematic constraints into account that suppress jet quenching in nuclear collisions below RHIC ($\sqrt{s}=200$ AGeV) energies.

nucl-th↗
arXiv2000

Jets and produced particles in pp collisions from SPS to RHIC energies for nuclear applications

Higher-order pQCD corrections play an important role in the reproduction of data at high transverse momenta in the energy range 20 GeV $ \leq \sqrt{s} \leq 200$ GeV. Recent calculations of photon and pion production in $pp$ collisions yield detailed information on the next-to-leading order contributions. However, the application of these results in proton-nucleus and nucleus-nucleus collisions is not straightforward. The study of nuclear effects requires a simplified understanding of the output of these computations. Here we summarize our analysis of recent calculations, aimed at handling the NLO results by introducing process and energy-dependent $K$ factors.

nucl-th↗
arXiv1999

Quark liberation and coalescence at CERN SPS

The mischievous linear coalescence approach to hadronization of quark matter is shown to violate strangeness conservation in strong interactions. The simplest correct quark counting is shown to coincide with the non-linear algebraic coalescence rehadronization model, ALCOR. The non-linearity of the ALCOR model is shown to cancel from its simple predictions for the relative yields of (multi-)strange baryons. We prove, model independently, that quark degrees of freedom are liberated before hadron formation in 158 AGeV central Pb + Pb collisions at CERN SPS.

hep-ph↗
arXiv1999

Hadronization with a confining equation of state

We present a fast hadronization model for the constituent quark plasma (CQP) produced in relativistic heavy ion collisions at SPS. The model is based on rate equations and on a confining equation of state inspired by the string phenomenology. We display the time evolution of the relevant physical quantities during the hadronization process and the final hadron multiplicities. The results indicate that the hadronization of CQP is fast.

hep-ph↗
arXiv1998

Strange hyperon and antihyperon production from quark and string-rope matter

Hyperon and antihyperon production is investigated using two microscopical models: {\bf (1)} the fast hadronization of quark matter as given by the ALCOR model; {\bf (2)} string formation and fragmentation as in the HIJING/B model. We calculate the particle numbers and momentum distributions for Pb+Pb collisions at CERN SPS energies in order to compare the two models with each other and with the available experimental data. We show that these two theoretical approaches give similar yields for the hyperons, but strongly differ for antihyperons.

hep-ph↗
arXiv1998

Hadronization of massive quark matter

We present a fast hadronization model for the constituent quark plasma (CQP) produced in relativistic heavy ion collisions at SPS. The model is based on rate equations and on an equation of state inspired by the string phenomenology. This equation of state has a confining character. We display the time evolution of the relevant physical quantities during the hadronization process and the final hadron multiplicities. The results indicate that the hadronization of CQP is fast.

hep-ph↗
arXiv1998

Hadronization in Heavy-Ion Reactions

We present a model of fast hadronization of constituent quark matter in relativistic heavy ion collisions based on rate equations and capture cross sections in non-relativistic potential. We utilize a thermodynamically consistent approach with a non-ideal equation of state including correlation terms based on string phenomenology. We investigate strange and non-strange particle ratios observed in CERN SPS experiments.

hep-ph↗
arXiv1996

Particle Spectra from the ALCOR Model

We introduce the Transchemistry Model as a dynamical extension of the Algebraic Coalescence Rehadronization (ALCOR) model in describing the hadronization of quark matter which is expected to be produced in relativistic heavy ion collisions. Results are presented for CERN SPS NA49 Pb+Pb experiment calculating hadron multiplicities and momentum spectra. The freeze-out properties of different hadrons are characterized by similar temperature, density and flow profiles in cylindrically symmetric geometry.

hep-ph↗
arXiv1996

Confinement and Entropy in Heavy Ion Collisions

We introduce a kinetical description of the hadronization of semi-deconfined quark matter produced in heavy ion collisions. A minimal microscopic model is considered in which the produced quarks and anti-quarks are redistributed into hadrons according to the additive quark model. Assuming thermalized quark matter and hadron matter we determine the appropriate parameters to describe the properties of both matter before and after hadronization. We find an adiabatic hadronization.

hep-ph↗
arXiv1996

Numerical Study of Spectrum and HBT Radii for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems

This study is devoted to a detailed numerical testing of the analytical results obtained recently for the $M_t$-scaling of the parameters of the Bose-Einstein correlation functions. Numerical testing of analytical results for the spectrum is also performed, since the geometrical sizes are folded into the momentum distribution in the scaling limiting case. The analytical results are shown to be valid in a wider rapidity-range than thought before.

hep-ph↗
arXiv1995

Strangeness Production in Chemically Non-Equilibrated Parton Plasma

Strangeness production was investigated during the equilibration of a gluon dominated parton plasma produced at RHIC and LHC energies. The time evolution of parton densities are followed by a set of rate equations in a 1-dimensional expanding system. The strangeness production will depend on the initial chemical equilibration level and in our case the parton densities will remain far from the full equilibrium. We investigate the influence of gluon fragmentation on final strangeness content.

hep-ph↗
arXiv1995

Strange Hadrons from the ALCOR Rehadronization Model

Hadron multiplicities --- especially for strange particles --- are calculated in the framework of the algebraic coalescence rehadronization model (ALCOR), which counts for redistribution of quarks into hadrons for relativistic heavy-ion collisions. The influence of Bjorken flow on the final hadronic composition are incorporated in the model. A comparison is made with the CERN SPS NA35 $S+S$ and $p+p$ experiments. The analysis of these experiments with ALCOR shows a strangeness enhancement for S+S collisions and a possible formation of a sort of semi-deconfined state of the matter. Predictions for Pb+Pb collisions (NA49) are also presented.

hep-ph↗
arXiv1994

Are There Top Quarks In Superdense Hybrid Stars?

It is examined whether primordial top quarks from the Big Bang could survive under natural conditions till present days. Hybrid quark-neutron stars, with dense enough core to maintain the existence of top quarks, is discussed. In this paper only final states are investigated. Zero temperature quark-lepton matter is modelled as as a gas of non-interacting particles. Local charge neutrality has been assumed in order to avoid volume interactions which would not make thermodynamical treatment possible.

astro-ph↗