Edwin Laermann

Thermal dilepton rate and electrical conductivity: An analysis of vector current correlation functions in quenched lattice QCD

We calculate the vector current correlation function for light valence quarks in the deconfined phase of QCD. The calculations have been performed in quenched lattice QCD at T ≃ 1.45Tc for four values of the lattice cut-off on lattices up to size 128 3 × 48. This allows to perform a continuum extrapolation of the correlation function in the Euclidean time interval 0.2 ≤ τT ≤ 0.5, which extends to the largest temporal separations possible at finite temperature, to better than 1% accuracy. In this interval, at the value of the temperature investigated, we find that the vector correlation function never deviates from the free correlator for massless quarks by more than 9%. We also determine the first two non-vanishing thermal moments of the vector meson spectral function. The second thermal moment deviates by less than 7% from the free value. With these constraints, we then proceed to extract information on the spectral representation of the vector correlator and discuss resulting consequences for the electrical conductivity and the thermal dilepton rate in the plasma phase.

Freeze-out Conditions in Heavy Ion Collisions from QCD Thermodynamics

We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range 150 MeV ≤ T ≤ 170 MeV the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%-15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.

Heavy quark potentials in quenched QCD at high temperature

Heavy quark potentials are investigated at high temperatures. The temperature range covered by the analysis extends from

Strangeness at high temperatures: from hadrons to quarks

T

The interquark potential: SU(2) colour gauge theory with fermions

values just below the deconfinement temperature up to about

Microscopic origin of U-A(1) symmetry violation in the high temperature phase of QCD

{4T}_{c}

Signatures of charmonium modification in spatial correlation functions

in the deconfined phase. We simulated the pure gauge sector of QCD on lattices with temporal extents of 4, 6, and 8, with spatial volumes of

A study of finite temperature gauge theory in (2+1) dimensions

{32}^{3}.

The quark mass and μ dependence of the QCD chiral critical point

On the smallest lattice a tree level improved action was employed, while in the other two cases the standard Wilson action was used. Below

Hadron Properties just before Deconfinement

{T}_{c}