Sequential charmonium dissociation

Finite temperature lattice QCD indicates that the charmonium ground state J/psi can survive in a quark-gluon plasma up to 1.5 T_c or more, while the excited states chi_c and psi-prime are dissociated just above T_c. We assume that the chi_c suffers the same form of suppression as that observed for the psi-prime in SPS experiments, and that the directly produced J/psi is unaffected at presently available energy densities. This provides a parameter-free description of J/psi and psi-prime suppression which agrees quite well with that observed in SPS and RHIC data.Comment: 10 pages, 8 figure

Glueball enhancement by color de-confinement

High energy heavy ion collisions lead to the formation of a strong coupling de-confined phase in which the lightest glueballs are numerous and stable. We analyze how their properties manifest themselves in experimental spectra and show that they provide a good signature for color de-confinement.Comment: 9 pages, 4 figure

Topological transitions in the euclidean 2d U(1)-Higgs model

The two-dimensional U(1)-gauged Higgs model is studied on an euclidean lattice of size $L_1\times L_2$, where the temperature $T=L_2^{-1}$ is of the order of the sphaleron mass. The simulation parameters are taken from zero temperature results. By comparison with classical and semiclassical results I discuss, whether the sphaleron transition rate can be extracted from the behavior of the Chern-Simons number and from the formation of vortices in an euclidean simulation at high temperatures.Comment: Talk presented at LATTICE96(topology), 3 pages, latex2e, 3 postscript figures, uses packages epsfig and espcrc

Eigenvalue distribution of the Dirac operator at finite temperature with (2+1)-flavor dynamical quarks using the HISQ action

We report on the behavior of the eigenvalue distribution of the Dirac operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We calculate the eigenvalue density at several values of the temperature close to the pseudocritical temperature. For this study we use gauge field configurations generated on lattices of size $32^3 \times 8$ with two light quark masses corresponding to pion masses of about 160 and 115 MeV. We find that the eigenvalue density below $T_c$ receives large contributions from near-zero modes which become smaller as the temperature increases or the light quark mass decreases. Moreover we find no clear evidence for a gap in the eigenvalue density up to 1.1$T_c$. We also analyze the eigenvalue density near $T_c$ where it appears to show a power-law behavior consistent with what is expected in the critical region near the second order chiral symmetry restoring phase transition in the massless limit.Comment: 7 pages, 7 figures, talk presented at the XXIX International Symposium on Lattice Field Theory, July 10-16 2011, Squaw Valley, Lake Tahoe, California, US

String Breaking and Quarkonium Dissociation at Finite Temperatures

Recent lattice studies of string breaking in QCD with dynamical quarks determine the in-medium temperature dependence of the heavy quark potential. Comparing this to the binding energies of different quarkonium states, we check if these can decay into open charm/beauty in a confined hadronic medium. Our studies indicate in particular that the chi_c and the psi dissociate into open charm below the deconfinement point.Comment: 8 pages LaTeX, 4 figure

Deconfinement Through Chiral Transition In 2 Flavour QCD

We propose that in QCD with dynamical quarks, colour deconfinement occurs when an external field induced by the chiral condensate strongly aligns the Polyakov loop. This effect sets in at the chiral symmetry restoration temperature $T_{\chi}$ and thus makes deconfinement and chiral symmetry restoration coincide. The predicted singular behavior of Polyakov loop susceptibilities at $T_{\chi}$ is shown to be supported by finite temperature lattice calculations.Comment: Talk given at Lattice 2000 (Finite Temperature), 4 pages, 6 EPS-figure

The scalar glueball spectrum

We discuss scenarios for scalar glueballs using arguments based on sum rules, spectral decomposition, the $\frac{1}{N_c}$ approximation, the scales of the strong interaction and the topology of the flux tubes. We analyze the phenomenological support of those scenarios and their observational implications. Our investigations hint a rich low lying glueball spectrum.Comment: 11 pages: New title, figure, table and a more detailed comparison with experiment