New Higgs decays to axion-like particles

TL;DR

This paper explores rare Higgs boson decays into multiple muons, photons, and jets mediated by a light scalar, constraining their probabilities with current and future collider data, and proposing new analysis strategies.

Contribution

It introduces new collider analysis methods for rare Higgs decays involving a light scalar, improving sensitivity estimates for current and future LHC runs.

Findings

Current LHC data can probe branching ratios down to 10^{-5} to 10^{-8}.

High-Luminosity LHC can improve sensitivity by an order of magnitude.

Several unexplored decay channels are identified for future searches.

Abstract

We investigate the interactions of a light scalar with the Higgs boson and second-generation fermions, which trigger new rare decays of the Higgs boson into $4\mu$, $2\mu 2\gamma$, $6\mu$ and $4\mu 2j$. We recast current LHC searches to constrain these decays and develop new collider analyses for those channels which are only poorly tested by existing studies. With the currently collected data we can probe branching ratios as small as $1.5 \times10^{-5}$, $8.7 \times10^{-5}$, $5.7 \times10^{-8}$ and $1.6 \times10^{-7}$, respectively. For the High-Luminosity LHC run, considered here to involve 3 ab$^{-1}$ of integrated luminosity, these numbers go down to $1.3 \times10^{-5}$, $2.0 \times10^{-6}$, $3.0 \times10^{-9}$ and $5.4 \times10^{-9}$, respectively. We also comment on other channels that remain still unexplored.