Optimizing pp → A → Z^∗h → ℓ+ℓ−b¯b searches at the LHC in the 2HDM Type-I with inverted hierarchy

Abstract

In this study, we investigate the Large Hadron Collider (LHC) search for the signal process pp → A →Z^∗h → ℓ+ℓ−b¯b (ℓ = e, µ) within the framework of the 2-Higgs-Doublet Model (2HDM) Type-I, consideringan Inverted Hierarchy (IH) scenario wherein the Standard Model (SM)-like Higgs boson H is heavier thanh (i.e., mh < mH = 125 GeV). We reproduce the dominant background distributions from a CMS analysisof pp → H → ZA → ℓ+ℓ−b¯b (for a on-shell Z), which we do for validation purposes, so that we canexplore different invariant mass selection criteria to enhance the signal significance of our target process.Specifically, we compare the CMS baseline cuts (70 GeV < mℓ+ℓ− < 110 GeV, no mb¯brestriction) withthe alternative selections 20 GeV < mℓ+ℓ− < 50 GeV with mb¯b < 100 GeV. The latter cuts are enforcedto account for the off-shellness of the Z^∗ boson and the low mass Higgs state in our case. We show thatthese modifications reduce drastically the dominant Drell-Yan (DY) and top-(anti)quark pair backgrounds,leading to a significant excess from the analysis of the reconstructed mℓ+ℓ−b¯binvariant mass in the illustrativeranges 145 GeV < mA < 150 GeV and 68 GeV < mh < 75 GeV. Our results demonstrate that such cutsenable effective signal discrimination, suggesting an optimized strategy in future searches for an establishedtopology but in a new kinematical regime, which is of particular relevance to the 2HDM Type-I with IH inits mass spectrum.

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Identifiers

ORCID for S. Moretti: orcid.org/0000-0002-8601-7246

ORCID for A.G. Akeroyd: orcid.org/0000-0001-7742-7035

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