Light Dark Matter through Assisted Annihilation

TL;DR

This paper explores a novel mechanism for light dark matter annihilation involving assisted processes with Standard Model-like species, enabling relic density reproduction at keV-MeV scales.

Contribution

It introduces the concept of assisted annihilation with scalar models, expanding possibilities for light dark matter candidates beyond standard scenarios.

Findings

Relic density achievable for keV-MeV dark matter with degenerate dark matter and assister.

Assisted annihilation opens new parameter space for light dark matter models.

Cosmological constraints are briefly discussed for these scenarios.

Abstract

In this paper we investigate light dark matter scenarios where annihilation to Standard Model particles at tree-level is kinematically forbidden. In such cases annihilation can be aided by massive Standard Model-like species, called {\it assisters}, in the initial state that enhances the available phase space opening up novel tree-level processes. We investigate the feasibility of such non-standard {\it assisted annihilation} processes to reproduce the observed relic density of dark matter. We present a simple scalar dark matter - scalar assister model where this is realised. We find that if the dark matter and assister are relatively degenerate the required relic density can be achieved for a keV-MeV scale dark matter. We briefly discuss the cosmological constraints on such dark matter scenarios.