Leptogenesis With Many Neutrinos

TL;DR

This paper explores how having many neutrinos, such as Kaluza-Klein excitations in extra dimensions, can relax the constraints on reheating temperature and neutrino mass scale in leptogenesis scenarios.

Contribution

It demonstrates that multiple neutrinos can significantly alter the bounds on reheating temperature and neutrino mass, introducing new possibilities in leptogenesis models.

Findings

Lower reheating temperature bounds are relaxed.

Upper neutrino mass bounds are lifted.

Extra-dimensional models with Kaluza-Klein neutrinos are viable.

Abstract

We consider leptogenesis in scenarios with many neutrino singlets. We find that the lower bound for the reheating temperature can be significantly relaxed with respect to the hierarchical three neutrino case. We further argue that the upper bound for the neutrino mass scale from leptogenesis gets significantly lifted in these scenarios. As a specific realization, we then discuss an extra-dimensional model, where the large number of neutrinos is provided by Kaluza-Klein excitations.