Leptogenesis with virtual Majorana neutrinos

TL;DR

This paper proposes a novel leptogenesis mechanism involving the decay of a scalar into virtual Majorana neutrinos, enabling precise quantum field theory calculations and demonstrating feasibility within a specific mass range.

Contribution

It introduces a new leptogenesis scheme using virtual Majorana neutrinos, simplifying calculations and addressing conceptual issues in the field.

Findings

A successful leptogenesis scenario is possible with a light scalar particle between 10^6 and 10^13 GeV.

The scheme allows quantum field theory techniques to compute lepton asymmetry without phenomenological approximations.

Embedding this mechanism into a grand unified theory appears challenging.

Abstract

We present a mechanism of leptogenesis based on the out-of-equilibrium decay of a scalar particle into heavy virtual Majorana neutrinos. This scheme presents many conceptual advantages over the conventional scenario of Fukugita and Yanagida. In particular, the standard techniques of quantum field theory can be used to compute the lepton asymmetry, without resorting to the phenomenological approximations usually made to describe unstable particles. This simplification allows us to address in a well-defined framework some issues raised in the recent literature. We also show, in a toy model, that a successful leptogenesis scenario is possible and requires a rather light scalar particle, $10^6 GeV < m < 10^{13} GeV$. A natural embedding of this scheme in a gauged unified theory encompassing the Majorana fermions seems however difficult.