Freeze-out of baryon number in low-scale leptogenesis
  Low-scale leptogenesis provides an economic and testable description of the
origin of the baryon asymmetry of the Universe. In this scenario, the baryon
asymmetry of the Universe is reprocessed from the lepton asymmetry by
electroweak sphaleron processes. Provided that sphalerons are fast enough to
maintain equilibrium, the values of the baryon and lepton asymmetries are
related to each other. Usually, this relation is used to find the value of the
baryon asymmetry at the time of the sphaleron freeze-out. To put in other
words, the formula which is valid only when the sphalerons are fast, is applied
at the moment when they are actually switched off. In this paper, we examine
the validity of such a treatment. To this end, we solve the full system of
kinetic equations for low-scale leptogenesis. This system includes equations
describing the production of the lepton asymmetry in oscillations of
right-handed neutrinos, as well as a separate kinetic equation for the baryon
asymmetry. We show that for some values of the model parameters, the
corrections to the standard approach are sizeable. We also present a feasible
improvement to the ordinary procedure, which accounts for these corrections.
