NLO thermal dilepton rate at non-zero momentum

Abstract

The vector channel spectral function and the dilepton production rate from a QCD plasma at a temperature above a few hundred MeV are evaluated up to next-to-leading order (NLO) including their dependence on a non-zero momentum with respect to the heat bath. The invariant mass of the virtual photon is taken to be in the range K^2 ~ (pi T)^2 ~ (1 GeV)^2, generalizing previous NLO results valid for K^2 >> (pi T)^2. In the opposite regime 0 < K^2 << (pi T)^2 the loop expansion breaks down, but agrees nevertheless in order of magnitude with a previous result obtained through resummations. Ways to test the vector spectral function through comparisons with imaginary-time correlators measured on the lattice are discussed.