TY  - THES
AB  - We develop a framework for obtaining rate coefficients in non-
linear kinetic equations for slowly evolving quantities in a non-
equilibrium system by matching real time correlation functions
of thermal fluctuations computed in an effective description to
those computed in thermal quantum field theory. We apply
this formalism to sterile neutrino occupancies and lepton minus
baryon numbers. After expanding in the sterile-neutrino Yukawa
couplings, the coefficients in the equations are written as real
time correlation functions of Standard Model operators. Our
kinetic equations are valid for an arbitrary number of sterile
neutrinos of any mass spectrum. They can be used to describe,
e.g., low-scale leptogenesis via neutrino oscillations, or sterile
neutrino dark matter production in the Higgs phase. We apply
the formula for linear coefficients to the equilibration of right-
handed electrons in the symmetric phase of the Standard Model,
which happens relatively late in the history of the Universe due
to the smallness of the electron Yukawa coupling. We compute
the equilibration rate at leading order in the Standard Model
couplings by including gauge interactions, the top Yukawa- and
the Higgs self-interaction. The dominant contribution is due to
2 -> 2 particle scattering, even though the rate of (inverse) Higgs
decays is strongly enhanced by multiple soft scattering which is
included by Landau-Pomeranchuk-Migdal (LPM) resummation.
Our numerical result for the equilibration rate is substantially
larger than approximations presented in previous literature. We
find that the equilibration of right-handed electrons takes place at
temperatures at which also low-scale leptogenesis can be realized,
and we argue that in this case the two processes do not decouple.
DA  - 2020
DO  - 10.4119/unibi/2941694
LA  - eng
PY  - 2020
TI  - Low-scale leptogenesis and right-handed electrons
UR  - https://nbn-resolving.org/urn:nbn:de:0070-pub-29416943
Y2  - 2024-11-22T09:17:53
ER  -