Hot Leptogenesis

TL;DR

This paper explores a novel 'hot leptogenesis' scenario where the right-handed neutrino sector reaches kinetic equilibrium at high temperatures, potentially resolving fine-tuning issues in standard leptogenesis models.

Contribution

It introduces the concept of hot leptogenesis, analyzes the conditions for equilibrium, and compares its parameter space with standard models, highlighting its advantages.

Findings

Hot leptogenesis can operate at higher temperatures than standard models.

It alleviates neutrino and Higgs mass fine-tuning problems.

The model's viability depends on specific reheating and equilibrium conditions.

Abstract

We investigate a class of leptogenesis scenarios in which the sector containing the lightest right-handed neutrino establishes kinetic equilibrium at a temperature $T_{N_1} > T_\text{SM}$, where $T_\text{SM}$ is the temperature of the Standard Model sector. We study the reheating processes which realise this "hot leptogenesis" and the conditions under which kinetic and chemical equilibrium can be maintained. We derive and solve two sets of evolution equations, depending on the presence of chemical equilibrium within the hot sector, and numerically solve these for benchmark scenarios. We compare the viable parameter space of this model with standard leptogenesis scenarios with a thermal initial condition and find that hot leptogenesis resolves the neutrino and Higgs mass fine-tuning problems present in the standard scenario.