Lepton asymmetry rate from quantum field theory: NLO in the hierarchical limit

Understand

The rates for generating a matter-antimatter asymmetry in extensions of the Standard Model (SM) containing right-handed neutrinos are the most interesting and least trivial coefficients in the rate equations for baryogenesis through thermal leptogenesis.

• We obtain a relation of these rates to finite-temperature real-time correlation functions, similar to the Kubo formulas for transport coefficients.
• Then we consider the case of hierarchical masses for the sterile neutrinos.
• At leading order in their Yukawa couplings we find a simple master formula which relates the rates to a single finite temperature three-point spectral function.