Damping of energetic gluons and quarks in high-temperature QCD.

Abstract

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