344 research outputs found

    Relativistic hydrodynamics with strangeness production

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    The relativistic hydrodynamic approach is used to describe production of strangeness and/or heavy quarks in ultrarelativistic heavy ion reactions. Production processes are important ingredients of dissipative effects in the hadronic liquid. Beyond viscosity also chemo- and thermo-diffusion processes are considered. This also allows to specify chemical and thermal freeze-out conditions.Comment: v.2 with minor editorial corrections, 7 pages, talk given on the SQM2007 conference, Levoca, June 24-29, 2007. To appear in the proceceeding: Journal of Physics

    Probability distributions in statistical ensembles with conserved charges

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    The probability distributions for charged particle numbers and their densities are derived in statistical ensembles with conservation laws. It is shown that if this limit is properly taken, then the canonical and grand canonical ensembles are equivalent. This equivalence is proven on the most general probability distribution level

    The Best Predictions in Experimental Biology are Critical and Persuasive

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    A powerful way to evaluate scientific explanations (hypotheses) is to test the predictions that they make. In this way, predictions serve as an important bridge between abstract hypotheses and concrete experiments. Experimental biologists, however, generally receive little guidance on how to generate quality predictions. Here, we identify two important components of good predictions – criticality and persuasiveness – which relate to the ability of a prediction (and the experiment it implies) to disprove a hypothesis or to convince a skeptic that the hypothesis has merit. Using a detailed example, we demonstrate how striving for predictions that are both critical and persuasive can speed scientific progress by leading us to more powerful experiments. Finally, we provide a quality control checklist to assist students and researchers as they navigate the hypothetico-deductive method from puzzling observations to experimental tests

    Entropy Production in Relativistic Hydrodynamics

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    The entropy production occurring in relativistic hydrodynamical systems such as the quark-gluon plasma (QGP) formed in high-energy nuclear collisions is explored. We study mechanisms which change the composition of the fluid, i.e. particle production and/or chemical reactions, along with chemo- and thermo-diffusion. These effects complement the conventional dissipative effects of shear viscosity, bulk viscosity, and heat conductivity.Comment: 15 pages; LaTex. Accepted for publication in Physics Letters B. - Two typos corrected and one reference adde

    Probability distributions in statistical ensembles with conserved charges

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    The probability distributions for charged particle numbers and their densities are derived in statistical ensembles with conservation laws. It is shown that if this limit is properly taken then the canonical and grand canonical ensembles are equivalent. This equivalence is proven on the most general, probability distribution level.Comment: 5 pages. A little bit shorter version due to some editorial and language changes. To be published in Phys. Rev.

    Properties of an equilibrium hadron gas subjected to the adiabatic longitudinal expansion

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    We consider an ideal gas of massive hadrons in thermal and chemical equilibrium. The gas expands longitudinally in an adiabatic way. This evolution for a baryonless gas reduces to a hydrodynamic expansion. Cooling process is parametrized by the sound velocity. The sound velocity is temperature dependent and is strongly influenced by hadron mass spectrum.Comment: 7pages, 7 figures-- uucoded file of figures appended at the end, separated from the paper by lines with many dashe

    The canonical partition function for relativistic hadron gases

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    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.Comment: 10 pages, 2 figures; submitted for publication in EPJ

    Pion Number Fluctuations and Correlations in the Statistical System with Fixed Isospin

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    The statistical system of pions with zero total isospin is studied. The suppression effects for the average yields due to isospin conservation are the same for π0\pi^0, π+\pi^+ and π−\pi^-. However, a behavior of the corresponding particle number fluctuations are different. For neutral pions there is the enhancement of the fluctuations, whereas for charged pions the isospin conservation suppresses fluctuations. The correlations between the numbers of charged and neutral pions are observed for finite systems. This causes a maximum of the total pion number fluctuations for small systems. The thermodynamic limit values for the scaled variances of neutral and charged pions are calculated. The enhancements of the fluctuations due to Bose statistics are found and discussed
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