Boosting invisible searches via $\boldsymbol{ZH}$: From the Higgs Boson to Dark Matter Simplified Models

TL;DR

This paper investigates Higgs boson production with a Z boson at the LHC, analyzing its potential to constrain Dark Matter models through invisible decay searches, and compares collider limits with non-collider bounds.

Contribution

It demonstrates the significance of loop-induced effects in Higgs+Z searches for Dark Matter and evaluates the channel's constraining power on simplified Dark Matter models with scalar and pseudo-scalar mediators.

Findings

Loop effects impact Higgs to invisible decay limits.

The channel constrains mediator couplings to Standard Model fermions.

Collider bounds are competitive with non-collider constraints for certain parameter ranges.

Abstract

Higgs boson production in association with a $Z$-boson at the LHC is analysed, both in the Standard Model and in Simplified Model extensions for Dark Matter. We focus on $H\rightarrow$invisibles searches and show that loop-induced components for both the signal and background present phenomenologically relevant contributions to the $\mathcal{BR}(H\rightarrow\textit{inv})$ limits. In addition, the constraining power of this channel to Simplified Models for Dark Matter with scalar and pseudo-scalar mediators $\phi$ and $A$ is discussed and compared with non-collider constraints. We find that with $100~fb^{-1}$ of LHC data, this channel provides competitive constraints to the non-collider bounds, for most of the parameter space we consider, bounding the universal Standard Model fermion-mediator strength at $g_v < 1$ for moderate masses in the range of ${100~\text{GeV}<m_{\phi/A}<400}$ GeV.