19 research outputs found
Interpolation of hard and soft dilepton rates
Strict next-to-leading order (NLO) results for the dilepton production rate
from a QCD plasma at temperatures above a few hundred MeV suffer from a
breakdown of the loop expansion in the regime of soft invariant masses M^2 <<
(pi T)^2. In this regime an LPM resummation is needed for obtaining the correct
leading-order result. We show how to construct an interpolation between the
hard NLO and the leading-order LPM expression. The final numerical results are
presented in a tabulated form, suitable for insertion into hydrodynamical
codes.Comment: 16 pages. v2: wordings clarifie
Right-handed neutrino production rate at T > 160 GeV
The production rate of right-handed neutrinos from a Standard Model plasma at
a temperature above a hundred GeV has previously been evaluated up to NLO in
Standard Model couplings (g ~ 2/3) in relativistic (M ~ pi T) and
non-relativistic regimes (M >> pi T), and up to LO in an ultrarelativistic
regime (M < gT). The last result necessitates an all-orders resummation of the
loop expansion, accounting for multiple soft scatterings of the nearly
light-like particles participating in 1 2 reactions. In this paper we
suggest how the regimes can be interpolated into a result applicable for any
right-handed neutrino mass and at all temperatures above 160 GeV. The results
can also be used for determining the lepton number washout rate in models
containing right-handed neutrinos. Numerical results are given in a tabulated
form permitting for their incorporation into leptogenesis codes. We note that
due to effects from soft Higgs bosons there is a narrow intermediate regime
around M ~ g^{1/2} T in which our interpolation is phenomenological and a more
precise study would be welcome.Comment: 26 pages. v2: minor clarifications, published versio