Electroweak-scale resonant leptogenesis

Abstract

We study minimal scenarios of resonant leptogenesis near the electroweak phase transition. These models offer a number of testable phenomenological signatures for low-energy experiments and future high-energy colliders. Our study extends previous analyses of the relevant network of Boltzmann equations, consistently taking into account effects from out of equilibrium sphalerons and single lepton flavors. We show that the effects from single lepton flavors become very important in variants of resonant leptogenesis, where the observed baryon asymmetry in the Universe is created by lepton-to-baryon conversion of an individual lepton number, for example, that of the $\ensuremath{\tau}$-lepton. The predictions of such resonant $\ensuremath{\tau}$-leptogenesis models for the final baryon asymmetry are almost independent of the initial lepton-number and heavy neutrino abundances. These models accommodate the current neutrino data and have a number of testable phenomenological implications. They contain electroweak-scale heavy Majorana neutrinos with appreciable couplings to electrons and muons, which can be probed at future ${e}^{+}{e}^{\ensuremath{-}}$ and ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ high-energy colliders. In particular, resonant $\ensuremath{\tau}$-leptogenesis models predict sizable $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay, as well as $e$- and $\ensuremath{\mu}$-number-violating processes, such as $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ and $\ensuremath{\mu}\ensuremath{\rightarrow}e$ conversion in nuclei, with rates that are within reach of the experiments proposed by the MEG and MECO collaborations.