https://doi.org/10.1140/epjc/s10052-019-6537-6
Regular Article - Theoretical Physics
Elliptic flow and 
of 
mesons at FAIR comparing the UrQMD hybrid model and the coarse-graining approach
1
Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, 60438, Frankfurt am Main, Germany
2
Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, 60438, Frankfurt am Main, Germany
3
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291, Darmstadt, Germany
4
John von Neumann Institute for Computing, Forschungszentrum Jülich, 52425, Jülich, Germany
5
Present address: Department of Physics, University of Jyvaskyla, P.O. Box 35, FI-40014, Jyvaskyla, Finland
6
Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
* e-mail: gabriele.g.inghirami@jyu.fi
Received:
27
April
2018
Accepted:
27
December
2018
Published online:
21
January
2019
We present a study of the elliptic flow and of and 
mesons in Au+Au collisions at FAIR energies. We propagate the charm quarks and the mesons following a previously applied Langevin dynamics. The evolution of the background medium is modeled in two different ways: (I) we use the UrQMD hydrodynamics + Boltzmann transport hybrid approach including a phase transition to QGP and (II) with the coarse-graining approach employing also an equation of state with QGP. The latter approach has previously been used to describe di-lepton data at various energies very successfully. This comparison allows us to explore the effects of partial thermalization and viscous effects on the charm propagation. We explore the centrality dependencies of the collisions, the variation of the decoupling temperature and various hadronization parameters. We find that the initial partonic phase is responsible for the creation of most of the 
mesons elliptic flow and that the subsequent hadronic interactions seem to play only a minor role. This indicates that mesons elliptic flow is a smoking gun for a partonic phase at FAIR energies. However, the results suggest that the magnitude and the details of the elliptic flow strongly depend on the dynamics of the medium and on the hadronization procedure, which is related to the medium properties as well. Therefore, even at FAIR energies the charm quark might constitute a very useful tool to probe the quark–gluon plasma and investigate its physics.
© The Author(s), 2019
