We study the evolution of heavy quarkonium states with temperature in a Quark Gluon Plasma (QGP) by evaluating the in-medium Q-Q T −matrix within a reduced Bethe-Salpeter equation in both S− and P −wave channels. The underlying interaction kernel is extracted from recent finite-temperature QCD lattice calculations of the singlet free energy of a Q-Q pair. The bound states are found to gradually move above the Q-Q threshold after which they rapidly dissolve in the hot system. The T −matrix approach is particularly suited to investigate these mechanisms as it provides a unified treatment of bound and scattering states including threshold effects and the transition to the (perturbative) continuum. We apply the T −matrix to calculate Q-Q spectral functions as well as pertinent Euclidean-time correlation functions which are compared to results from lattice QCD. A detailed analysis reveals large sensitivities to the interplay of bound and scattering states, to temperature dependent threshold energies and to the "reconstructed" correlator used for normalization. We furthermore investigate the impact of finite-width effects on the single-quark propagators in the QGP as estimated from recent applications of heavy-quark rescattering to RHIC data.

We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse momentum spectrum and rapidity distribution of charm quarks from Fixed-Order Next-to-Leading Logarithm (FONLL) calculations. The produced charm quarks scatter in the quark-gluon plasma (QGP) with the off-shell partons whose masses and widths are given by the Dynamical Quasi-Particle Model (DQPM), which reproduces the lattice QCD equation-of-state in thermal equilibrium. The relevant cross sections are calculated in a consistent way by employing the effective propagators and couplings from the DQPM. Close to the critical energy density of the phase transition, the charm quarks are hadronized into D mesons through coalescence and fragmentation. The hadronized D mesons then interact with the various hadrons in the hadronic phase with cross sections calculated in an effective lagrangian approach with heavyquark spin symmetry. Finally, the nuclear modification factor RAA and the elliptic flow v2 of D 0 mesons from PHSD are compared with the experimental data from the STAR Collaboration for Au+Au collisions at √ sNN =200 GeV. We find that in the PHSD the energy loss of D mesons at high pT can be dominantly attributed to partonic scattering while the actual shape of RAA versus pT reflects the heavy-quark hadronization scenario, i.e. coalescence versus fragmentation. Also the hadronic rescattering is important for the RAA at low pT and enhances the D-meson elliptic flow v2.

The φ meson spectrum, which in vacuum is dominated by its coupling to theKK system, is modified in nuclear matter. Following a model based on chiral SU (3) dynamics we calculate the φ meson selfenergy in nuclear matter considering the K andK in-medium properties. For the latter we use the results of previous calculations which account for S− and P −wave kaon-nucleon interactions based on the lowest order meson-baryon chiral effective Lagrangian, and this leads to a dressing of the kaon propagators in the medium. In addition, a set of vertex corrections is evaluated to fulfill gauge invariance, which involves contact couplings of the φ meson to S−wave and P −wave kaon-baryon vertices. Within this scheme the mass shift and decay width of the φ meson in nuclear matter are studied.

We study charm production in Pb+Pb collisions at √ sNN =2.76 TeV in the Parton-Hadron-StringDynamics transport approach and the charm dynamics in the partonic and hadronic medium. The charm quarks are produced through initial binary nucleon-nucleon collisions by using the PYTHIA event generator taking into account the (anti-)shadowing incorporated in the EPS09 package. The produced charm quarks interact with off-shell massive partons in the quark-gluon plasma and are hadronized into D mesons through coalescence or fragmentation close to the critical energy density, and then interact with hadrons in the final hadronic stage with scattering cross sections calculated in an effective Lagrangian approach with heavy-quark spin symmetry. The PHSD results show a reasonable RAA and elliptic flow of D mesons in comparison to the experimental data for Pb+Pb collisions at √ sNN = 2.76 TeV from the ALICE Collaboration. We also study the effect of temperature-dependent off-shell charm quarks in relativistic heavy-ion collisions. We find that the scattering cross sections are only moderately affected by off-shell charm degrees of freedom. However, the position of the peak of RAA for D mesons depends on the strength of the scalar partonic forces which also have an impact on the D meson elliptic flow. The comparison with experimental data on the RAA suggests that the repulsive force is weaker for off-shell charm quarks as compared to that for light quarks. Furthermore, the effects from radiative charm energy loss appear to be low compared to the collisional energy loss up to transverse momenta of ∼ 15 GeV/c.

Abstract. We compute the charm drag and diffusion coefficients in a hot pion gas, such as is formed in a Heavy Ion Collision after the system cools sufficiently to transit into the hadron phase. We fully exploit Heavy Quark Effective Theory (with both D and D * mesons as elementary degrees of freedom during the collision) and Chiral Perturbation Theory, and employ standard unitarization to reach higher temperatures. We find that a certain friction and shear diffusion coefficients are almost p 2 -independent at fixed temperature which simplifies phenomenological analysis. At the higher end of reliability of our calculation, T ≃ 150 MeV, we report a charm relaxation length λc ≃ 40 fm, in agreement with the model estimate of He, Fries and Rapp.

The strongly coupled phase of Yang-Mills plasma with arbitrary gauge group is studied in a T matrix approach. The existence of lowest-lying glueballs, interpreted as bound states of two transverse gluons (quasiparticles in a many-body setup), is analyzed in a nonperturbative scattering formalism with the input of lattice-QCD static potentials. Glueballs are actually found to be bound up to 1.3 T c . Starting from the T-matrix, the plasma equation of state is computed by resorting to a formulation of statistical mechanics (Dashen et al.) and favorably compared to quenched lattice data. Special emphasis is put on SUðNÞ gauge groups, for which analytical results can be obtained in the large-N limit, and predictions for a G 2 gauge group are also given in this work.

Based on a prior determination of the φ selfenergy in a nuclear medium we perform a theoretical study of inclusive φ photoproduction in nuclei, looking at the A dependence of the cross sections for different φ momenta. We find sizeable reductions in the nuclear cross sections with respect to the elementary one, using a φ selfenergy which implies a width about six times the free one at normal nuclear density. The calculations are done to match the set up for an ongoing experiment at SPring8/Osaka which should provide valuable information on the renormalization of the φ properties in nuclei.

We study the properties of K andK mesons in nuclear matter at finite temperature from a chiral unitary approach in coupled channels that incorporates the s and p waves of the kaon-nucleon interaction. The in-medium solution accounts for Pauli blocking effects, mean-field binding on all the baryons involved, and π and kaon self-energies. We calculate K andK (off-shell) spectral functions and single-particle properties. TheK effective mass gets lowered by about −50 MeV in cold nuclear matter at saturation density and by half this reduction at T = 100 MeV. The p-wave contribution to theK optical potential, due to , , and * excitations, becomes significant for momenta larger than 200 MeV/c and reduces the attraction felt by theK in the nuclear medium. TheK spectral function spreads over a wide range of energies, reflecting the melting of the (1405) resonance and the contribution of Y N −1 components at finite temperature. In the KN sector, we find that the low-density theorem is a good approximation for the K self-energy close to saturation density due to the absence of resonance-hole excitations. The K potential shows a moderate repulsive behavior, whereas the quasiparticle peak is considerably broadened with increasing density and temperature. We discuss the implications for the decay of the φ meson at GSI Schwerionen Synchrotron energies as well as in the future Facility for Antiproton and Ion Research project.