Prospects for detecting the rare heavy Higgs decay $H\to h\gamma\gamma$ through the $H\to b\bar{b}\gamma\gamma$ channel at the LHC

TL;DR

This paper explores the potential to detect a rare heavy Higgs decay into a Standard Model Higgs and two photons at the LHC, highlighting its significance for different 2HDM types and mass ranges.

Contribution

It introduces the decay channel $H\to h\gamma\gamma$ as a promising signature for heavy Higgs detection and discusses its role in distinguishing 2HDM types and improving event rates.

Findings

Potential observation of $H\to h\gamma\gamma$ at the HL-LHC up to 950 GeV for type-II 2HDM.

Detection prospects up to 650 GeV for Lepton Specific and Flipped 2HDMs.

Detection up to 350 GeV for type-I 2HDM.

Abstract

We study the decay of a heavy CP-even neutral Higgs into an on-shell Standard Model-like Higgs boson and two photons, $H\to h\gamma\gamma$, in the two-Higgs doublet model. We argue that the decay channel $H\to h\gamma\gamma$, followed by the decay of the Standard Model Higgs $h\rightarrow b\bar b$, could be observed at the 5$\sigma$ level at the High-Luminosity LHC for masses of the heavy Higgs up to 950 GeV for the type-II, 650 GeV for the Lepton Specific and the Flipped 2HDMs, and 350 GeV for the type-I. We also discuss the possible role of the decay $H\to h\gamma\gamma$ in discriminating among different types of 2HDMs and in enhancing the total number of events in the final state $H\rightarrow b\bar b \gamma\gamma$ compared to the cascade decay $H\to hh$ followed by $h\to\gamma\gamma$ $h\to b\bar{b}$ with identical final state (although with different kinematical distributions).