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Register a new userStrangeness production in hadronic models and recombination models
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Authors
Gunnar Graf
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We present recent results on the production, spectra and elliptic flow of strange particles in dynamic simulations employing hadronic degrees of freedom and from recombination models. The main focus will be on the Ultra-relativistic Molecular Dynamics (UrQMD) Boltzmann approach to relativistic heavy ion collisions and a hybrid approach with intermediate hydrodynamic evolution based on UrQMD (available for download as UrQMD v3.3). Compared to the standard binary collision approach, an enhancement of the strange particle particle yields is found in the hybrid approach due to the assumption of local equilibration. The production origins of the Phi-meson in the hybrid approach are studied in further detail. We also present results on the transverse momentum spectra of baryon to meson ratios of strange particles. Due to the approximate energy independent scaling of this ratio as a function of p_T we argue, that a maximum in these spectra may not be a unique sign for quark coalescence but can be understood in terms of flow and fragmentation.
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The results of the microscopic transport calculations of $bar p$-nucleus interactions within a GiBUU model are presented. The dominating mechanism of hyperon production is the strangeness exchange processes $bar K N to Y pi$ and $bar K N to Xi K$. The calculated rapidity spectra of $Xi$ hyperons are significantly shifted to forward rapidities with respect to the spectra of $S=-1$ hyperons. We argue that this shift should be a sensitive test for the possible exotic mechanisms of $bar p$-nucleus annihilation. The production of the double $Lambda$-hypernuclei by $Xi^-$ interaction with a secondary target is calculated.
We review recent developments in the field of microscopic transport model calculations for ultrarelativistic heavy ion collisions. In particular, we focus on the strangeness production, for example, the phi-meson and its role as a messenger of the early phase of the system evolution. Moreover, we discuss the important effects of the (soft) field properties on the multiparticle system. We outline some current problems of the models as well as possible solutions to them.
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