Coscattering/Coannihilation Dark Matter in a Fraternal Twin Higgs Model

TL;DR

This paper investigates the relic density of twin neutrino dark matter in a fraternal twin Higgs model, exploring coannihilation and coscattering processes, and assesses experimental constraints and future detection prospects.

Contribution

It introduces a comprehensive method to calculate relic density considering both coannihilation and coscattering in the twin neutrino dark matter scenario.

Findings

Relic density can match observed dark matter abundance in various parameter regions.

Coscattering phase can dominate under certain freeze-out conditions.

Experimental constraints and future detection methods are outlined for model viability.

Abstract

Dark matter candidates arise naturally in many models that address the hierarchy problem. In the fraternal twin Higgs model which could explain the absence of the new physics signals at the Large Hadron Collider (LHC), there are several viable dark matter candidates. In this paper we study the twin neutrino in the mass range $\sim$ 0.1--10 GeV as the dark matter. The thermal relic density is determined by the interplay of several annihilation and scattering processes between the twin neutrino, twin tau, and twin photon, depending on the order of the freeze-out temperatures of these processes. Besides the common coannihilation scenario where the relic density is controlled by the twin tau annihilation, it can realize the recently discovered coscattering phase if the scattering of the twin neutrino into the twin tau freezes out earlier than the twin tau annihilation. We also provide a method to calculate the thermal relic density in the intermediate regime where both coannihilation and coscattering processes contribute to the determination of the dark matter density. We show that the right amount of dark matter can be obtained in various scenarios in different regions of the parameter space. The current experimental constraints and future probes into the parameter space from direct detections, cosmological and astrophysical bounds, dark photon searches, and displaced decays at colliders, are discussed.