Browsing by Author "Oeschler, H"

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    On the chemical equilibration of strangeness-exchange reactions in heavy-ion collisions
    (2005) Cleymans, J; Forster, A; Oeschler, H; Redlich, K; Uhlig, F
    The strangeness-exchange reaction π + Y ↔ K− + N is shown to be the dynamical origin of chemical saturation and equilibration for K− production in heavy-ion collisions up to beam energies of 10 AGeV. The hyperons occurring in this process are produced in association with K+ in baryon–baryon and meson–baryon interactions. This connection is demonstrated by the ratio of K−/K+ which does not vary with centrality and shows a linear correlation with the yield of pions per participant. At incident energies above AGS this correlation no longer holds due to the change in the production mechanism of kaons.
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    Transition from baryonic to mesonic freeze-out
    (2005) Cleymans, J; Oeschler, H; Redlich, K; Wheaton, S
    The recently discovered sharp peak in the K+/π+ ratio in relativistic heavy-ion collisions is discussed in the framework of the statistical model. In this model a rapid change is expected as the hadronic gas undergoes a transition from a baryon-dominated to a meson-dominated gas. The transition occurs at a temperature T=140MeV and baryon chemical potential μB=410MeV corresponding to an incident energy of sNN=8.2GeV. The maximum in the Λ/π ratio is well reproduced by the statistical model, but the change in the K+/π+ ratio is much less pronounced than the one observed by the NA49 Collaboration. The calculated smooth increase of the K−/π− ratio and the shape of the Ξ−/π+ and Ω−/π+ ratios exhibiting maxima at different incident energies is consistent with the presently available experimental data. We conclude that the measured particle ratios with 20–30% deviations agree with a hadronic freeze-out scenario. These deviations seem to occur just in the transition from baryon-dominated to meson-dominated freeze-out.