Sterile Neutrinos from Dark Matter: A $\nu$ Nightmare?

TL;DR

This paper develops a comprehensive framework and open-source tools to predict observable signals from dark matter annihilation or decay into sterile neutrinos, covering a wide mass range and improving upon standard simulation methods.

Contribution

It introduces a complete method to calculate decay spectra and branching ratios for sterile neutrinos across various mass scales, addressing limitations of existing simulation tools.

Findings

Provides detailed spectra for photons, positrons, and neutrinos from sterile neutrino decays.

Highlights differences between these signals and standard dark matter annihilation channels.

Offers open-source code for community use and further research.

Abstract

We provide a comprehensive study of observable spectra from dark matter pair-annihilation or decay into sterile (right-handed) neutrinos. This occurs, for instance, in neutrino portal dark matter models, where a sterile neutrino acts as the portal between dark matter and the Standard Model sector. The subsequent decays of right-handed neutrinos produce detectable Standard Model particles, notably photons, positrons, and neutrinos. We study the phenomenology of models where the right-handed neutrino masses are below the GeV scale, as well as models where they are at, or significantly heavier than, the TeV scale. In both instances, and for different reasons, the standard tools, including Monte Carlo simulations, are both inadequate and inaccurate. We present the complete framework to compute the relevant branching ratios for right-handed neutrino decays and the spectra of secondary photons, positrons, and neutrinos for a broad range of dark matter and right-handed neutrino masses. We discuss the general features of such signals, and compare the spectra to standard signals from dark matter annihilation/decay into bottom quarks. Additionally, we provide open source code1 that can be used to compute such spectra. The code is available at https://github.com/LoganAMorrison/blackthorn.