Leptogenesis during Axion Relaxation after Inflation

TL;DR

This paper proposes a minimal alternative to thermal leptogenesis where an axion-like field after inflation creates conditions for baryogenesis, independent of heavy neutrino CP phases, requiring high reheating temperatures.

Contribution

It introduces a novel leptogenesis mechanism driven by axion-like fields, differing from thermal models by its insensitivity to neutrino sector parameters.

Findings

Baryon asymmetry generated is independent of heavy neutrino CP phases.

Requires reheating temperature of at least 10^12 GeV.

Compatible with grand unification scale neutrino masses.

Abstract

In this talk, I present a novel and minimal alternative to thermal leptogenesis, which builds upon the assumption that the electroweak gauge bosons are coupled to an axion-like scalar field, as it is, for instance, the case in certain string compactifications. The motion of this axion-like field after the end of inflation generates an effective chemical potential for leptons and antileptons, which, in the presence of lepton number-violating scatterings mediated by heavy Majorana neutrinos, provides an opportunity for baryogenesis via leptogenesis. In contrast to thermal leptogenesis, the final baryon asymmetry turns out to be insensitive to the masses and CP-violating phases in the heavy neutrino sector. Moreover, the proposed scenario requires a reheating temperature of at least O(10^12) GeV and it is, in particular, consistent with heavy neutrino masses close the scale of grand unification. This talk was given in February 2015 at HPNP 2015 at Toyama University and is based on recent work (arXiv:1412.2043 [hep-ph]) in collaboration with A. Kusenko and T. T. Yanagida.