Measuring rare and exclusive Higgs boson decays into light resonances

TL;DR

This paper assesses the LHC's ability to detect rare Higgs decays into light resonances via hadronic channels, providing limits on branching ratios and implications for 2HDM models.

Contribution

It introduces a novel analysis of Higgs decays into light resonances using jet substructure observables and extrapolates sensitivities to high luminosity LHC data.

Findings

Branching ratio limits of about 2% for h→ZA and h→Zηc at 95% CL.

Searches for h→ZA are complementary to existing measurements.

Constraints on 2HDM Type 1 parameter space.

Abstract

We evaluate the LHC's potential of observing Higgs boson decays into light elementary or composite resonances through their hadronic decay channels. We focus on the Higgs boson production processes with the largest cross sections, $pp\to h$ and $pp\to h+\mathrm{jet}$, with subsequent decays $h \to ZA$ or $h\to Z\,\eta_c$, and comment on the production process $pp\to hZ$. By exploiting track-based jet substructure observables and extrapolating to $3000~\mathrm{fb}^{-1}$ we find ${\cal BR}(h \to ZA) \simeq {\cal BR}(h \to Z \eta_c) \lesssim 0.02$ at 95% CL. We interpret this limit in terms of the 2HDM Type 1. We find that searches for $h\to ZA$ are complementary to existing measurements and can constrain large parts of the currently allowed parameter space.