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Dilepton production by dynamical quasiparticles in the strongly interacting quark gluon plasma

The dilepton production by the constituents of the strongly interacting quark-gluon-plasma (sQGP) is addressed. In order to make quantitative predictions at realistically low plasma temperatures (O(T_c)), experimentally relevant low dilepton mass (O(1 GeV)) and strong coupling (alphaS=0.5-1), we take into account not only the higher order pQCD reaction mechanisms, but also the non-perturbative spectral functions (off-shellness) and self-energies of the quarks, anti-quarks and gluons thus going beyond the leading twist. For this purpose, our calculations utilize parametrizations of the non-perturbative propagators for quarks and gluons provided by the dynamical quasi-particle model (DQPM) matched to reproduce lattice data. The DQPM describes QCD properties in terms of single-particle Green's functions (in the sense of a two-particle irreducible approach) and leads to the notion of the constituents of the sQGP being effective quasiparticles, which are massive and have broad spectral functions (due to large interaction rates). In the present work, we derive the off-shell cross sections of dilepton production in the reactions q+qbar->l^+l^- (Drell-Yan mechanism), q+qbar->g+l^+l^- (quark annihilation with the gluon Bremsstrahlung in the final state), q(qbar)+g->q(qbar)+l^+l^- (gluon Compton scattering), g->q+qbar+l^+l^- and q(qbar)->q(qbar)+g+l^+l^- (virtual gluon decay, virtual quark decay) in the sQGP by dressing the quark and gluon lines in the perturbative diagrams with the DQPM propagators for quarks and gluons.