Boosting the production of sterile neutrino dark matter with self-interactions

TL;DR

This paper explores how sterile neutrino self-interactions mediated by a scalar can enhance dark matter production, revealing new parameter space regions and production regimes that could be tested by future observations.

Contribution

It introduces a detailed analysis of sterile neutrino self-interactions across various mediator masses, identifying four distinct production regimes and expanding viable dark matter parameter space.

Findings

Four production regimes identified, including partial thermalization and resonant production.

Self-interactions open new parameter space for sterile neutrino dark matter.

Potential for future observational tests of these new regions.

Abstract

Sterile neutrinos are well-motivated and simple dark matter (DM) candidates. However, sterile neutrino DM produced through oscillations by the Dodelson-Widrow mechanism is excluded by current $X$-ray observations and bounds from structure formation. One minimal extension, that preserves the attractive features of this scenario, is self-interactions among sterile neutrinos. In this work, we analyze how sterile neutrino self-interactions mediated by a scalar affect the production of keV sterile neutrinos for a wide range of mediator masses. We find four distinct regimes of production characterized by different phenomena, including partial thermalization for low and intermediate masses and resonant production for heavier mediators. We show that significant new regions of parameter space become available which provide a target for future observations.