DAMPING OF ENERGETIC GLUONS AND QUARKS IN HIGH-TEMPERATURE QCD

When a gluon or a quark is sent through the hot QCD plasma it acquires a damping rate that is given by gamma(p) = cg2ln(1/g)T + O(g2T) for \p\ >> gT. We show that very simple arguments suffice to fix the numerical coefficient c in this expression and to show that the O(g2T) contribution is incalculable in perturbation theory without further assumptions. For QCD with N(c) colors we find c(g) = + N(c)/4-pi for gluons and c(q) = + (N(c)2-1)/8-pi-N(c) for quarks, in agreement with more detailed calculations of Pisarski et al. but not with those of Lebedev et al. The simplicity of the calculation permits a direct verification of the gauge invariance and the physical sign of the result.