Probing light fermiophobic Higgs boson via diphoton jets at the HL-LHC

Abstract

In this study, we explore the phenomenological signatures associated with a light fermiophobic Higgs boson, hf, within the type-I two-Higgs-doublet model at the HL-LHC. Our meticulous parameter scan illuminates an intriguing mass range for mhf, spanning [1,10] GeV. This mass range owes its viability to substantial parameter points, largely due to the inherent challenges of detecting the soft decay products of hf at contemporary high-energy colliders. Given that this light hf ensures Br(hf→γγ)≃1, Br(H±→hfW±)≃1, and MH±≲330 GeV, we propose a golden discovery channel: pp→hfH±→γγγγℓ±ν, where ℓ± includes e± and μ±. However, a significant obstacle arises as the two photons from the hf decay mostly merge into a single jet due to their proximity within ΔR<0.4. This results in a final state characterized by two jets, rather than four isolated photons, thus intensifying the QCD backgrounds. To tackle this, we devise a strategy within to identify jets with two leading subparticles as photons, termed diphoton jets. Our thorough detector-level simulations across 18 benchmark points predominantly show signal significances exceeding the 5σ threshold at an integrated luminosity of 3 ab−1. Furthermore, our approach facilitates accurate mass reconstructions for both mhf and MH±. Notably, in the intricate scenarios with heavy charged Higgs bosons, our application of machine learning techniques provides a significant boost in significance. Published by the American Physical Society 2024