Freeze-in leptogenesis without the need for right-handed neutrino oscillations

TL;DR

This paper introduces a new leptogenesis mechanism within the type-I seesaw model that operates at GeV-scale right-handed neutrinos without requiring oscillations or CP violation, making it experimentally testable.

Contribution

It proposes a novel leptogenesis process that functions with a single RHN at GeV scale, expanding the viable parameter space for baryogenesis.

Findings

Successful baryogenesis achievable without RHN oscillations

Mechanism works with a single RHN at GeV scale

Large parameter space for viable leptogenesis

Abstract

We present an experimentally testable leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino (RHN) masses around the GeV scale. The mechanism takes place in a cosmological background with an asymmetry between right-handed electrons and left-handed positrons generated at high temperatures, and does not require oscillations between RHNs or any CP violation in the RHN sector. In contrast to standard leptogenesis via freeze-in, our mechanism works even in the presence of a single RHN around the GeV scale. The mechanism is illustrated for the minimal type-I seesaw with two RHNs, where we show that successful baryogenesis via leptogenesis is viable in large regions of parameter space even without a small mass splitting between the RHNs.