Could a light Higgs boson illuminate the dark sector?

TL;DR

This paper systematically analyzes how a new light neutral particle could affect the decay width of a light Higgs boson, exploring signatures with missing energy and setting constraints on new physics models.

Contribution

It provides a comprehensive effective field theory framework for analyzing the impact of various light particles on Higgs decays, including all relevant interactions.

Findings

Tight model-independent constraints on masses and couplings of new light states.

Analysis of Higgs decay modes with missing energy, including invisible and semi-visible channels.

Guidelines for experimental searches for light dark sector particles via Higgs decays.

Abstract

The impact a new neutral light particle of spin 0, 1/2, 1, or 3/2 could have on the tiny width of a light Higgs boson is systematically analyzed. To this end, we include all the relevant effective interactions, whether renormalizable or not, and review the possible signatures in the Higgs decay modes with missing energy. This includes the fully invisible Higgs boson decay, as well as modes with SM gauge boson or fermions in the final state. In many cases, simply preventing these modes from being dominant suffices to set tight model-independent constraints on the masses and couplings of the new light states.