The dark side of the Higgs boson

TL;DR

This paper explores the possibility that the Higgs boson has a significant invisible decay width, potentially hiding a heavier Higgs from current searches, and proposes a method to measure this width using the h to ZZ to 4l lineshape.

Contribution

It introduces a novel approach to infer the Higgs' invisible decay width from the lineshape analysis and discusses constraints on dark matter models from Higgs and direct detection data.

Findings

A heavy Higgs could evade current bounds if it has a large invisible decay width.

The proposed lineshape method can help detect or constrain invisible Higgs decays.

Minimal dark matter models are strongly constrained unless relic density constraints are relaxed.

Abstract

Current limits from the Large Hadron Collider exclude a standard model-like Higgs mass above 150 GeV, by placing an upper bound on the Higgs production rate. We emphasize that, alternatively, the limit could be interpreted as a lower bound on the total decay width of the Higgs boson. If the invisible decay width of the Higgs is of the same order as the visible decay width, a heavy Higgs boson could be consistent with null results from current searches. We propose a method to infer the invisible decay of the Higgs by using the width of the measured h to ZZ to 4l lineshape, and study the effect on the width extraction due to a reduced signal strength. Assuming the invisible decay product is the dark matter, we show that minimal models are tightly constrained by limits from Higgs searches at the LHC and direct detection experiments of dark matter, unless the relic density constraint is relaxed.