We determine the analytic expression of the damping rates for very soft moving quarks in an expansion to second order in powers of their momentum in the context of QCD at high temperature. The calculation is performed using the hard-thermal-loop-summed perturbation scheme. We describe the range of validity of the expansion and make a comparison with other calculations, particularly those using a magnetic mass as a shield from infrared sensitivity.We discuss the possible occurrence of infrared divergences in our results and argue that they are due to magnetic sensitivity. pacs: 11.10.Wx 12.38.-t 12.38.Bx 12.38.Mh keywords: hard thermal loops. soft quark damping. infrared sensitivity.
We investigate the infrared properties of the next-to-leading-order dispersion relations in scalar quantum electrodynamics at high temperature in the context of hard-thermal-loop perturbation theory. Specifically, we determine the damping rate and the energy for scalars with ultrasoft momenta. We show by explicit calculations that an early external-momentum expansion, before the Matsubara sum is performed, gives exactly the same result as a late one. The damping rate is obtained up to fourth order included in the ultrasoft momentum and the energy up to second order. The damping rate is found sensitive in the infrared whereas the energy not.
The long standing issue known as the hot QCD collinear singularity problem has been proven to rely on an incorrect sequence of two mathematical operations. Here, the original derivation of this problem is entirely revisited within the correct sequence, bringing to light new and unexpected conclusions.
The damping rate γt(p) of on-shell transverse gluons with ultrasoft momentum p is obtained in the context of next-to-leading-order hard-thermal-loop-summed perturbation of high-temperature massless quantum chromodynamics (QCD). It is obtained in an expansion to the second order in p. The first coefficient known in the literature is recovered, but that of order p2 is found to be divergent in the infrared. Divergences from light-like momenta do also occur but are circumvented. By carrying out similar calculations in the context of scalar quantum electrodynamics, it is shown that early and late external-momentum expansions yield identical results.
We determine the quark damping rates in the context of next-to-leading order hard-thermal-loop summed perturbation of high-temperature QCD where weak coupling is assumed. The quarks are ultrasoft. Three types of divergent behavior are encountered: infrared, light-cone and at specific points determined by the gluon energies. The infrared divergence persists and is logarithmic whereas the two others are circumvented.
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