K^{*} vector meson resonances dynamics in heavy-ion collisions

We study the strange vector meson ($K^*, \bar K^*$) dynamics in relativistic heavy-ion collisions based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees-of-freedom, a phase transition from hadronic to partonic matter - Quark-Gluon-Plasma (QGP) - and a dynamical hadronization of quarks and antiquarks as well as final hadronic interactions. We investigate the role of in-medium effects on the $K^*, \bar K^*$ meson dynamics by employing Breit-Wigner spectral functions for the $K^*$'s with self-energies obtained from a self-consistent coupled-channel G-matrix approach. Furthermore, we confront the PHSD calculations with experimental data for p+p, Cu+Cu and Au+Au collisions at energies up to $\sqrt{{s}_{NN}} = 200$~GeV. Our analysis shows that at relativistic energies most of the final $K^*$s (observed experimentally) are produced during the late hadronic phase, dominantly by the $K+ \pi \to K^*$ channel, such that the fraction of the $K^*$s from the QGP is small and can hardly be reconstructed from the final observables. The influence of the in-medium effects on the $K^*$ dynamics at RHIC energies is rather modest due to their dominant production at low baryon densities (but high meson densities), however, it increases with decreasing beam energy. Moreover, we find that the additional cut on the invariant mass region of the $K^*$ further influences the shape and the height of the final spectra. This imposes severe constraints on the interpretation of the experimental results.