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The effect of the chiral symmetry restoration (CSR) on observables from heavy-ion collisions is studied in the energy range √sNN=3-20 GeV within the Parton- Hadron-String Dynamics (PHSD) transport approach. The PHSD includes the deconfinement phase transition as well as essential aspects of CSR in the dense and hot hadronic medium, which are incorporated in the Schwinger mechanism for the hadronic particle production. We adopt different parametrizations of the nuclear equation of state from the non-linear σ - ω model, which enter in the computation of the quark scalar density for the CSR mechanism, in order to estimate the uncertainty in our calculations. For the pion-nucleon Σ-term we adopt Σπ ≈ 45 MeV which corresponds to a 'world average'. Our systematic studies show that chiral symmetry restoration plays a crucial role in the description of heavy-ion collisions at √sNN=3-20 GeV, realizing an increase of the hadronic particle production in the strangeness sector with respect to the non-strange one. We identify particle abundances and rapidity spectra to be suitable probes in order to extract information about CSR, while transverse mass spectra are less sensitive ones. Our results provide a microscopic explanation for the "horn" structure in the excitation function of the K+/π+ ratio: the CSR in the hadronic phase produces the steep increase of this particle ratio up to √sNN ≈ 7 GeV, while the drop at higher energies is associated to the appearance of a deconfined partonic medium. [ABSTRACT FROM AUTHOR]

We investigate the properties of the QCD matter across the deconfinement phase transition in the scope of the parton-hadron string dynamics (PHSD) transport approach. We present here in particular the results on the electromagnetic radiation, i.e. photon and dilepton production, in relativistic heavy-ion collisions. By comparing our calculations for the heavy-ion collisions to the available data, we determine the relative importance of the various production sources and address the possible origin of the observed strong elliptic flow v2 of direct photons. We argue that the different centrality dependence of the hadronic and partonic sources for direct photon production in nucleus-nucleus collisions can be employed to shed some more light on the origin of the photon v2 "puzzle". While the dilepton spectra at low invariant mass show in-medium effects like an enhancement from multiple baryonic resonance formation or a collisional broadening of the vector meson spectral functions, the dilepton yield at high invariant masses (above 1.1 GeV) is dominated by QGP contributions for central heavy-ion collisions at ultrarelativistic energies. This allows to have an independent view on the parton dynamics via their electromagnetic massive radiation. [ABSTRACT FROM AUTHOR]

Recent STAR data for the directed flow of protons, antiprotons and charged pions obtained within the beam energy scan program are analyzed within the Parton- Hadron-String-Dynamics (PHSD/HSD) transport models. Both versions of the kinetic approach are used to clarify the role of partonic degrees of freedom. The PHSD results, simulating a partonic phase and its coexistence with a hadronic one, are roughly consistent with the STAR data. Generally, the semi-qualitative agreement between the measured data and model results supports the idea of a crossover type of quark-hadron transition which softens the nuclear EoS but shows no indication of a first-order phase transition. Furthermore, the directed flow of kaons and antikaons is evaluated in the PHSD/HSD approaches from √sNN ≈ 3 - 200 GeV which shows a high sensitivity to hadronic potentials in the FAIR/NICA energy regime √sNN ≤ 8 GeV. [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]