Leptogenesis in crossing and runaway regimes.
Original version
Hohenegger, A. & Kartavtsev, A. (2014) Leptogenesis in crossing and runaway regimes. Journal of high energy physics 10.1007/JHEP07(2014)130Abstract
We study the impact of effective thermal masses and widths on resonant leptogenesis. We identify two distinct possibilities which we refer to as ‘crossing’ and ‘runaway’
regimes. In the runaway regime the mass difference grows monotonously with temperature, whereas it initially decreases in the crossing regime, such that the effective masses
become equal at some temperature. Following the conventional logic the source of the
asymmetry would vanish in the latter case. Using non-equilibrium quantum field theory,
we analytically demonstrate that the vanishing of the difference of the effective masses does
however neither imply a suppression nor a strong enhancement of the source for the lepton
asymmetry. In the vicinity of the crossing point the asymmetry calculated in an (improved)
Boltzmann limit develops a spurious peak, which signals the breakdown of the quasiparticle
approximation. In the exact result this spurious enhancement is compensated by coherent transitions between the two mass shells. Despite the breakdown of the quasiparticle
approximation off-shell contributions remain negligibly small even at the crossing point.
Description
This is an open access article under the CC BY license, originally published in the journal Higher Energy Physics in 2014.