Effective theories for Dark Matter interactions and the neutrino portal paradigm

TL;DR

This paper develops an effective-theory framework for multi-component dark sectors interacting with the Standard Model, focusing on the neutrino portal scenario where dark matter couples primarily to neutrinos, predicting monochromatic neutrino signals.

Contribution

It introduces a comprehensive categorization of effective operators for dark sectors with neutral mediators, emphasizing the neutrino portal scenario and its unique phenomenological features.

Findings

Large parameter space compatible with current constraints

Neutrino lines as a distinctive signature of the neutrino portal

Suppressed couplings to SM particles except neutrinos

Abstract

In this article we discuss a general effective-theory description of a multi-component dark sector with an unspecified non-trivial symmetry and its interactions with the Standard Model generated by the exchange of heavy mediators. We then categorize the relevant effective operators given the current experimental sensistivity where the underlying theory is weakly coupled and renormalizable, with neutral mediators: either scalars or fermions. An interesting scenario resulting from this categorization is the neutrino portal, where only fermion mediators are present, and where the dark sector consists of fermions and scalars such that the lightest dark particle is a fermion, this scenario is characterized by having naturally suppressed couplings of the DM to all SM particles except the neutrinos and has received little attention in the literature. We find that there is a wide region in parameter space allowed by the current experimental constraints (relic abundance, direct and indirect detection limits); the cleanest signature of this paradigm is the presence of monochromatic neutrino lines with energy equal to that of the DM mass, but experimental sensitivity would have to be improved significantly before this can be probed.