On the full Boltzmann equations for Leptogenesis

TL;DR

This paper investigates the impact of using full Boltzmann equations, instead of integrated ones, on leptogenesis calculations, revealing significant deviations in lepton asymmetry predictions, especially in weak washout regimes.

Contribution

It introduces the use of full kinetic Boltzmann equations for leptogenesis, highlighting their effects on lepton asymmetry evolution and washout processes, which were previously underestimated.

Findings

Full Boltzmann equations increase washout effects on initial asymmetry.

In soft leptogenesis, the final asymmetry can differ by up to a factor of four.

Deviations are especially significant in weak washout regimes.

Abstract

We consider the full Boltzmann equations for standard and soft leptogenesis, instead of the usual integrated Boltzmann equations which assume kinetic equilibrium for all species. Decays and inverse decays may be inefficient for thermalising the heavy-(s)neutrino distribution function, leading to significant deviations from kinetic equilibrium. We analyse the impact of using the full kinetic equations in the case of a previously generated lepton asymmetry, and find that the washout of this initial asymmetry due to the interactions of the right-handed neutrino is larger than when calculated via the integrated equations. We also solve the full Boltzmann equations for soft leptogenesis, where the lepton asymmetry induced by the soft SUSY-breaking terms in sneutrino decays is a purely thermal effect, since at T=0 the asymmetry in leptons cancels the one in sleptons. In this case, we obtain that in the weak washout regime (K ~< 1) the final lepton asymmetry can change up to a factor four with respect to previous estimates.