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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 qq→γ*, qq→γ*+g and qg→γ*q(qg→γ*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 ∼1 GeV/fm3) 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 mT spectra at intermediate masses (1 GeV ≤ M ≤ 3 GeV) is approximately reproduced. [ABSTRACT FROM AUTHOR]

We investigate meson electroproduction off complex nuclei in the kinematic regime of the HERMES experiment using a semi-classical transport model which is based on the Boltzmann­Uehling­Uhlenbeck (BUU) equation. We discuss coherence length and color transparency effects in exclusive ρ0 production as well as hadron formation and attenuation of charged pions, kaons, protons and anti-protons in deep inelastic lepton scattering off nuclei. [ABSTRACT FROM AUTHOR]

The lifetime of heavy hypernuclei has been determined at COSY Ju¨lich making use of the (p,K)-reaction and the recoil-shadow technique based on the detection of fragments from the Λ-decay induced fission. Hypernuclei were produced by bombarding extremely thin U and Bi targets with protons of 1.5 GeV and 1.9 GeV kinetic energy. High luminosity was achieved due to the multi-pass technique with the target being exposed to the internal beam of COSY. Position sensitive low pressure MWPCs permitted clear identification of fission fragments based on energy loss and TOF information. The lifetime of hypernuclei was deduced from the position distributions of fission events in the shadow region and from the recoil momentum calculated within the BUU model. Values of 240±60 ps and 161±7(stat.)±14(syst.)ps were found with U and Bi-targets, respectively. The deduced production cross sections for hot hypernuclei prior to the evaporation process of σ=150[sub -80][sup +150] μb for U and 350±140 μb for Bi are in agreement with the theoretical predictions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present a transport theoretical analysis of hadron attenuation in deep inelastic lepton scattering (DIS) off complex nuclei in the kinematic regime of the HERMES experiment. The HERMES data indicate the presence of strong prehadronic final state interactions shortly after the elementary lepton-nucleon interaction. The contribution of such (pre-)hadronic final state interactions to the observed jet quenching in ultra-relaticistic heavy ion collisions (HIC) at RHIC is estimated under the assumption that a similar space-time picture for hadronization also holds in a hot hadronic medium. Our results show that an additional mechanism for jet quenching must be at work for most central collisions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]