Browsing by Author "Abbas, E"

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    Possible interrelations among chemical freeze-out conditions
    (WORLD SCIENTIFIC PUBL CO PTE LTD, 2016-03) Abbas, E; Mohamed, M. T; Habashy, D. M; El-Bakry, M. Y; Tawfik, A
    At thermal equilibrium, different chemical freeze-out conditions have been proposed so far. They have an ultimate aim of proposing a universal description for the chemical freeze-out parameters (T-ch and mu(b)), which are to be extracted from the statistical fitting of different particle ratios measured at various collision energies with calculations from thermal models. A systematic comparison between these conditions is presented. The physical meaning of each of them and their sensitivity to the hadron mass cuts are discussed. Based on availability, some of them are compared with recent lattice calculations. We found that most of these conditions are thermodynamically equivalent, especially at small baryon chemical potential. We propose that further crucial consistency tests should be performed at low energies. The fireball thermodynamics is another way of guessing conditions describing the chemical freeze-out parameters extracted from high-energy experiments. We endorse the possibility that the various chemical freeze-out conditions should be interpreted as different aspects of one universal condition.
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    Thermal Description of Particle Production in Au-Au Collisions at RHIC Energies (STAR)
    (PLEIADES PUBLISHING INC, 2015-07) Abbas, E; Tawfik, A
    The hadron ratios measured in central Au-Au collisions are analysed by means of Hadron Resonance Gas (HRG) model over a wide range of nucleon-nucleon center-of-mass energies, root S-NN = 7.7-200 GeV as offered by the RHIC Beam Energy Scan I (BES-I) (STAR Collaboration). The temperature and baryon chemical potential are deduced from fits of experimental ratios to thermal model calculations assuming chemical equilibrium. We find that the resulting freeze-out parameters using single hard-core value and point-like constituents of HRG are identical. This implies that the excluded-volume comes up with no effect on the extracted parameters. We compare the results with other studies and with the lattice QCD calculations. Various freeze-out conditions are confronted with the resulting data set. The effect of including new resonances is also analysed. At vanishing chemical potential, a limiting temperature was estimated, T-lim = 158.5 +/- 3 MeV.