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HK: Fachverband Physik der Hadronen und Kerne

HK 19: Schwerionenkollisionen und QCD Phasen

HK 19.3: Vortrag

Dienstag, 18. März 2014, 14:45–15:00, HZ 6

Investigating the transition between hydrodynamics and transport in heavy ion collision simulations — •Dmytro Oliinychenko and Hannah Petersen — Frankfurt Institute of Advanced Studies

One of the established ways to describe the dynamical evolution of heavy ion collisions theoretically is hydrodynamics with subsequent switching to transport, i.e. so-called hybrid models [1]. The switching process itself is organized as follows: at some predefined hypersurface the hydrodynamic evolution is stopped and particle distributions are generated according to the Cooper-Frye formula. Unavoidably, some particles from these distributions fly back into the hydrodynamic region. Such particles, which are also refered to as "negative contributions", are usually neglected in current hybrid approaches [2].

In the present study we present a systematic investigation of the negative contributions in a coarse-grained transport approach. Many UrQMD (Ultra-relativistic Quantum Molecular Dynamics) events are generated and the negative contributions calculated in a Cooper-Frye prescription are compared to the negative contributions based on the actual underlying particles. The other crucial point in hybrid approaches is the assumption of local equilibrium in the early stages of the collision. Therefore, we also show how fast local thermal equilibrium is reached in the UrQMD transport approach. The goal of this study is to extract a criterion for local thermalization.

[1] P. Huovinen, H. Petersen; EPJ A48 (2012)171 [2] H. Petersen, et al.; Phys.Rev. C78 (2008) 04490