  We study the equilibration of right-handed electrons in the symmetric phase
of the Standard Model. Due to the smallness of the electron Yukawa coupling, it
happens relatively late in the history of the Universe. 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 \to 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 is substantially larger than approximations presented in
previous literature.
