Sterile Neutrino Dark Matter as a Probe of Inflationary Reheating

TL;DR

This paper explores how sterile neutrino dark matter produced during inflationary reheating can be used to probe the reheating process, with potential constraints from future X-ray observations.

Contribution

It introduces a novel production mechanism for sterile neutrino dark matter during reheating and maps the viable parameter space, linking dark matter properties to inflationary reheating.

Findings

Sterile neutrino DM can be produced efficiently during reheating from inflaton decays.

Future X-ray observations can constrain the reheating temperature significantly.

The model evades current X-ray constraints while matching observed dark matter abundance.

Abstract

Sterile neutrinos offer a minimal and testable explanation for dark matter (DM), with their radiative decay actively searched for in X-ray observations. We show that cold sterile neutrino DM can be efficiently produced during reheating from inflaton decays with a tiny branching ratio, ${\rm BR}\lesssim 10^{-4}$. This production mechanism opens regions of parameter space where the active-sterile mixing is small enough to evade current X-ray constraints while reproducing the observed DM abundance. We systematically map the viable parameter space in terms of the sterile neutrino mass, mixing angle, inflaton mass, reheating temperature, and branching ratio. We further demonstrate that sterile neutrino DM can serve as a probe of inflationary reheating, with future X-ray observations capable of setting lower bounds on the reheating temperature several orders of magnitude above the existing bound from Big Bang Nucleosynthesis.