When the free energy density of QCD is expanded in a Taylor series in the chemical potential, µ, the coefficients are the non-linear quark number susceptibilities. We show that these depend on the prescription for putting chemical potential on the lattice, making all extrapolations in chemical potential prescription dependent at finite lattice spacing. To put bounds on the prescription dependence, we investigate the magnitude of the non-linear susceptibilities over a range of temperature, T , in QCD with two degenerate flavours of light dynamical quarks at lattice spacing 1/4T . The prescription dependence is removed in quenched QCD through a continuum extrapolation, and the dependence of the pressure, P , on µ is obtained.
We study screening correlators of quark-antiquark composites at T = 2Tc, where Tc is the QCD phase transition temperature, using overlap quarks in the quenched approximation of lattice QCD. As the lattice spacing is changed from 1/4T to a = 1/6T and 1/8T , we find that screening correlators change little, in contrast with the situation for other types of lattice fermions. All correlators are close to the ideal gas prediction at small separations. The long distance falloff is clearly exponential, showing that a parametrization by a single screening length is possible at distances z ≥ 1/T . The correlator corresponding to the thermal vector is close to the ideal gas value at all distances, whereas that for the thermal scalar deviates at large distances. This is examined through the screening lengths and momentum space correlators. There is strong evidence that the screening transfer matrix does not have reflection positivity.
Abstract:We summarize the theoretical description of charmonium and bottonium production in hadronic collisions and compare it to the available data from hadron-nucleon interactions. With the parameters of the theory established by these data, we obtain predictions for quarkonium production at RHIC and LHC energies.
The momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte Carlo techniques. The diffusion coefficient is extracted from the long-distance behavior of such a correlator. For temperatures T c < T & 2T c , our nonperturbative estimate of the diffusion coefficient is found to be very different from the leading-order perturbation theory and is in the right ballpark to explain the heavy quark flow seen by the PHENIX Collaboration at the RHIC experiment.
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