INFRARED SENSITIVITY OF SCREENING AND DAMPING IN A QUARK-GLUON PLASMA

All the next-to-leading order contributions to the quasiparticle dispersion laws of a quark-gluon plasma, which, because of infrared singularities, are sensitive to the magnetic-mass scale, are calculated using Braaten-Pisarski resummation. These relative-order-gln(g) corrections are shown here to contribute generally to the dynamical screening of gluonic fields with frequencies below the plasma frequency as well as to the damping of propagating gluonic and fermionic quasiparticles. In the limit of a vanishing wave vector the infrared singularities disappear, but in a way that raises the possibility for formally higher orders of the Braaten-Pisarski scheme to contribute equally at next-to-leading order when the wave vector is of the order of or less than the magnetic-mass scale. This is argued to be a problem in particular for the fermionic damping rate.