Dileptons from correlated D- and bar{D}-meson decays in the invariant mass range of the QGP thermal radiation using the UrQMD hybrid model

Relativistic heavy-ion collisions produce a hot and dense thermalized medium, that is expected to emit thermal radiation in form of dileptons. These dileptons are not affected by the strong force and are therefore a clean probe for the possible creation of a Quark Gluon Plasma (QGP). However, electroweak decays of open-charm mesons are expected to induce a substantial background in the invariant mass region between the $\phi$ and $J/\Psi$ peak ($1\,\text{GeV} \lesssim M_{\ell^+ \ell^-} \lesssim 3 \,\text{GeV}$) of the thermal QGP radiation. To evaluate this background radiation we apply a Langevin approach for the transport of charm quarks in the UrQMD (hydrodynamics + Boltzmann) hybrid model. Due to the inclusion of event-by-event fluctuations and a full (3+1)-dimensional hydrodynamic evolution, the UrQMD hybrid approach provides a more realistic model for the evolution of the matter produced in heavy ion collisions as compared to simple homogeneous fireball expansions usually employed before. As drag and diffusion coefficients we use a resonance approach for elastic heavy-quark scattering and assume a decoupling temperature of the charm quarks from the hot medium of $130\,\text{MeV}$. For the hadronization of the charm quarks we employ a coalescence approach at the decoupling temperature from the medium. In this letter we present our calculations of the D-meson correlations and the invariant mass spectra of the dilepton decays in heavy-ion collisions at FAIR, RHIC, and LHC energies using different interaction scenarios.