LHC signatures of a light pseudoscalar in a flipped two-Higgs scenario: the usefulness of boosted $b{\bar b}$ pairs

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Main Authors: Ghosh, Dilip Kumar, Mukhopadhyaya, Biswarup, Samanta, Sirshendu, Singh, Ritesh K.
Format: Preprint
Published: 2026
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author Ghosh, Dilip Kumar
Mukhopadhyaya, Biswarup
Samanta, Sirshendu
Singh, Ritesh K.
author_facet Ghosh, Dilip Kumar
Mukhopadhyaya, Biswarup
Samanta, Sirshendu
Singh, Ritesh K.
contents Similar to some other two-Higgs doublet models (2HDM), the flipped 2HDM admits of a light pseudoscalar physical state whose mass can be well below 50 GeV. The fact that the pseudoscalar decays dominantly into a $b{\bar b}$ pair makes its identification at the Large Hadron Collider (LHC) difficult. Moreover, the regions of the parameter space corresponding to a light pseudoscalar tend to jeopardize perturbativity at a rather low scale. One possibility that ameliorates this problem is to postulate that the light physical state has the admixture of an SU(2) singlet field. In such a situation, however, the production mode of the pseudoscalar along with a $Z$ (which provides a useful tag) gets suppressed. We have here chosen to fall back on the QCD-driven final state, namely, one or two jets, together with an energetic squeezed $b{\bar b}$-pair. We utilize boosted di-b-jet tagging techniques and a strategy based on boosted decision trees (BDT) to analyze the signals, considering all backgrounds and likely fakes (mostly from charmed quarks). We find that, including 10\% systematics, one can expect signal significance of 5-10$σ$ with an integrated luminosity of 3 $ab^{-1}$.
format Preprint
id arxiv_https___arxiv_org_abs_2604_06937
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle LHC signatures of a light pseudoscalar in a flipped two-Higgs scenario: the usefulness of boosted $b{\bar b}$ pairs
Ghosh, Dilip Kumar
Mukhopadhyaya, Biswarup
Samanta, Sirshendu
Singh, Ritesh K.
High Energy Physics - Phenomenology
Similar to some other two-Higgs doublet models (2HDM), the flipped 2HDM admits of a light pseudoscalar physical state whose mass can be well below 50 GeV. The fact that the pseudoscalar decays dominantly into a $b{\bar b}$ pair makes its identification at the Large Hadron Collider (LHC) difficult. Moreover, the regions of the parameter space corresponding to a light pseudoscalar tend to jeopardize perturbativity at a rather low scale. One possibility that ameliorates this problem is to postulate that the light physical state has the admixture of an SU(2) singlet field. In such a situation, however, the production mode of the pseudoscalar along with a $Z$ (which provides a useful tag) gets suppressed. We have here chosen to fall back on the QCD-driven final state, namely, one or two jets, together with an energetic squeezed $b{\bar b}$-pair. We utilize boosted di-b-jet tagging techniques and a strategy based on boosted decision trees (BDT) to analyze the signals, considering all backgrounds and likely fakes (mostly from charmed quarks). We find that, including 10\% systematics, one can expect signal significance of 5-10$σ$ with an integrated luminosity of 3 $ab^{-1}$.
title LHC signatures of a light pseudoscalar in a flipped two-Higgs scenario: the usefulness of boosted $b{\bar b}$ pairs
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2604.06937