Light dark Higgs boson in minimal sub-GeV dark matter scenarios

TL;DR

This paper explores the phenomenology and experimental constraints of light dark Higgs bosons in minimal sub-GeV dark matter models, highlighting detection prospects in current and future experiments.

Contribution

It introduces two minimal dark sector models with light dark Higgs bosons and analyzes their experimental constraints and detection prospects.

Findings

BBN and CMB constraints are relaxed in these models.

Future experiments like Xenon1T and LDMX can probe the entire relevant parameter space.

Dark Higgs bosons can be detected in proton beam-dump experiments.

Abstract

Minimal scenarios with light (sub-GeV) dark matter whose relic density is obtained from thermal freeze-out must include new light mediators. In particular, a very well-motivated case is that of a new "dark" massive vector gauge boson mediator. The mass term for such mediator is most naturally obtained by a "dark Higgs mechanism" which leads to the presence of an often long-lived dark Higgs boson whose mass scale is the same as that of the mediator. We study the phenomenology and experimental constraints on two minimal, self-consistent dark sectors that include such a light dark Higgs boson. In one the dark matter is a pseudo-Dirac fermion, in the other a complex scalar. We find that the constraints from BBN and CMB are considerably relaxed in the framework of such minimal dark sectors. We present detection prospects for the dark Higgs boson in existing and projected proton beam-dump experiments. We show that future searches at experiments like Xenon1T or LDMX can probe all the relevant parameter space, complementing the various upcoming indirect constraints from astrophysical observations.