Dileptons from the nonequilibrium Quark-Gluon Plasma

Abstract

According to the dynamical quasiparticle model (DQPM) -- matched to reproduce lattice QCD results in thermodynamic limit, -- the constituents of the strongly interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles (quarks and gluons) with broad spectral functions. In order to address the electromagnetic radiation of the sQGP, we derive off-shell cross sections of $q\bar{q}\to {\gamma }^{\ast }$, $q\bar{q}\to {\gamma }^{\ast }+g$ and $qg\to {\gamma }^{\ast }q$($\bar{q}g\to {\gamma }^{\ast }\bar{q}$) reactions taking into account the effective propagators for quarks and gluons from the DQPM. Dilepton production in In+In collisions at 158 AGeV is studied by implementing these processes into the parton-hadron-string dynamics (PHSD) transport approach. The microscopic PHSD transport approach describes the full evolution of the heavy-ion collision: from the dynamics of quasi-particles in the sQGP phase (when the local energy density is above $\sim 1$ GeV/fm${}^3$) through hadronization and to the following hadron interactions and off-shell propagation after the hadronization. A comparison to the data of the NA60 Collaboration shows that the low mass dilepton spectra are well described by including a collisional broadening of vector mesons, while the spectra in the intermediate mass range are dominated by off-shell quark-antiquark annihilation, quark Bremsstrahlung and gluon-Compton scattering in the nonperturbative QGP. In particular, the observed softening of the $m_T$ spectra at intermediate masses (1 GeV $\le M\le$ 3 GeV) is approximately reproduced.

8 pages, 8 figures, to be published in the Proceedings of the 26th Winter Workshop on `Nuclear Dynamics', Ochto Rios, Jamaica, 2-9 January, 2010

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Cited by in corpus (2)

• Kelvin-Helmholz instability in high energy heavy ion collisions
• Low-mass dilepton production through transport process in quark-gluon plasma