Speaker
Prof.
Harvey Meyer
(Johannes Gutenberg University Mainz)
Description
We investigate the emission rate of photons in a perfectly thermalized
quark-gluon plasma via lattice QCD correlation functions of the
electromagnetic current. The thermal correlation functions can be
split into a spatially longitudinal and a transverse part, and the
photon rate is determined by the transverse part, since the
longitudinal part vanishes at light-like kinematics. However, we
focus mostly on the difference of the transverse and longitudinal
parts, because this difference vanishes identically in the vacuum and
is therefore directly sensitive to thermal effects. We thus probe the
photon rate in the range of photon momenta between $\pi T/2$ and $2\pi
T$. The relevant Euclidean correlation functions are
computed with $N_f = 2$ O($a$) improved Wilson fermions in the high-temperature
phase and extrapolated to the continuum. In order to estimate the
photon rate, an ill-posed problem for the vector-channel spectral
function must be solved. Within a class of Pade-form spectral
functions describing in particular the diffusion pole, we determine
the subset that is not excluded by the lattice data and obtain from it
a range of possible photon emission rates. Comparisons are made with
the non-interacting spectral functions and with the well-known N=4
super-Yang-Mills spectral functions at infinite coupling obtained by
AdS/CFT methods.
Primary author
Prof.
Harvey Meyer
(Johannes Gutenberg University Mainz)
