Self-interacting freeze-in dark matter in a singlet doublet scenario

TL;DR

This paper explores a non-thermal dark matter production mechanism involving a scalar singlet and doublet fermions, highlighting how modified early universe cosmology can influence relic abundance and detection prospects.

Contribution

It introduces a scalar extended singlet doublet fermion model with self-interacting dark matter, analyzing the effects of strong coupling and alternative cosmological histories on relic abundance and collider signals.

Findings

Strongly coupled dark sector leads to dark thermal equilibrium and suppressed relic abundance.

Modified early universe cosmology can restore relic abundance to observed levels.

GeV-scale dark matter may be detectable at LHC via displaced vertex signatures.

Abstract

We examine the non-thermal production of dark matter in a scalar extended singlet doublet fermion model where the lightest admixture of the fermions constitutes a suitable dark matter candidate. The dark sector is non-minimal with the MeV scale singlet scalar, which is stable in the Universe lifetime and can mediate the self-interaction for the multi-GeV fermion dark matter mitigating the small scale structure anomalies of the Universe. If the dark sector is strongly coupled, it undergoes internal dark thermal equilibrium after freeze-in production, and we end up with suppressed relic abundance for the fermion dark matter in a radiation dominated Universe. In contrast, the presence of a modified cosmological phase in the early era drives the fermion dark matter to satisfy nearly the whole amount of observed relic. It also turns out that the assumption of an unconventional cosmological history can allow the GeV scale dark matter to be probed at LHC from displaced vertex signature with improved sensitivity.