Electromagnetic emissivity of hot and dense matter

In this study we investigate dilepton production in heavy-ion collisions from $\sqrt{s_{NN}}=8$ GeV to 5 TeV with a focus on the competition between the thermal QGP radiation and the semi-leptonic decays from correlated D—meson pairs. As a 'tool' we employ the parton-hadron-string dynamics (PHSD) transport approach incorporating for the first time a fully microscopic treatment of the charm dynamics and their semi-leptonic decays. We find that the dileptons from correlated D—meson decays dominate the 'thermal' radiation from the QGP in central Pb+Pb collisions at the intermediate masses (1.2 GeV < M < 3 GeV) for $\sqrt{s_{NN}}>40$ GeV, while for $\sqrt{s_{NN}}=5$ to 20 GeV the contribution from D,$\overline{D}$ decays to the intermediate mass dilepton spectra is subleading such that one should observe a rather clear signal from the QGP radiation. We, furthermore, study the p_T-spectra and the R_AA(p_T) of single electrons at different energies. (paper)