Abstract
We present a study of the elliptic flow and R_{AA} of text {D} and bar{text {D}} mesons in Au+Au collisions at FAIR energies. We propagate the charm quarks and the text {D} 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 text {D}/bar{text {D}} mesons elliptic flow and that the subsequent hadronic interactions seem to play only a minor role. This indicates that text {D}/bar{text {D}} 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.
Highlights
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 an equation of state with QGP
We find that the initial partonic phase is responsible for the creation of most of the D/Dmesons elliptic flow and that the subsequent hadronic interactions seem to play only a minor role
After a brief introduction to the bulk evolution models that we use, i.e. the UrQMD hybrid model [25–27] and the coarse graining approach [28], we shortly review the formalism of the relativistic Langevin propagation, we provide a basic overview of how we compute the transport coefficients, both for charm quarks and D mesons
Summary
J. C (2019) 79:52 collision energy in the range of the upcoming FAIR facility [21], and available at RHIC, within the Beam Energy scan program [22], and at NICA [23]. We adopt a Langevin propagation model, implicitly assuming that the heavy quark momentum transfer is much smaller than for the light partons, an approximation that at low collision energies should work reasonably well, while at RHIC and LHC energies it is really consistent only for bottom quarks [24]. After a brief introduction to the bulk evolution models that we use, i.e. the UrQMD hybrid model [25–27] and the coarse graining approach [28], we shortly review the formalism of the relativistic Langevin propagation, we provide a basic overview of how we compute the transport coefficients, both for charm quarks and D mesons. After showing and commenting the results of the simulations, we discuss how we might improve them
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