Thermal effects in freeze-in neutrino dark matter production

TL;DR

This paper investigates how thermal effects influence the production of sterile neutrino dark matter via freeze-in, revealing that such effects can enhance production efficiency beyond standard gauge interaction estimates.

Contribution

It introduces a detailed analysis of thermal effects on sterile neutrino production, applicable to various low-energy seesaw models with heavy neutrinos in equilibrium.

Findings

Thermal effects increase dark matter production compared to gauge-only calculations.

Freeze-in production can be more efficient when thermal effects are included.

The study provides a framework for analyzing sterile neutrino dark matter in early universe conditions.

Abstract

We present a detailed study of the production of dark matter in the form of a sterile neutrino via freeze-in from decays of heavy right-handed neutrinos. Our treatment accounts for thermal effects in the effective couplings, generated via neutrino mixing, of the new heavy neutrinos with the Standard Model gauge and Higgs bosons and can be applied to several low-energy fermion seesaw scenarios featuring heavy neutrinos in thermal equilibrium with the primordial plasma. We find that the production of dark matter is not as suppressed as to what is found when considering only Standard Model gauge interactions. Our study shows that the freeze-in dark matter production could be efficient.