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Probing the low mass pseudoscalar in the flipped two-Higgs-doublet model

Dilip Kumar Ghosh1,*, Biswarup Mukhopadhyaya2,†, Sirshendu Samanta2,‡, and Ritesh K. Singh2,§

  • *Contact author: tpdkg@iacs.res.in
  • †Contact author: biswarup@iiserkol.ac.in
  • ‡Contact author: ss21rs027@iiserkol.ac.in
  • §Contact author: ritesh.singh@iiserkol.ac.in
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Phys. Rev. D 112, 075035 – Published 17 October, 2025

DOI: https://doi.org/10.1103/nfzx-96x1

Abstract

The phenomenology of the flipped two-Higgs-doublet model (2HDM) is relatively less explored so far, as compared to the other, commonly discussed, types. It is found that this scenario, like several others, admits of a light neutral pseudoscalar A in the mass range 20–60 GeV, consistently with all current experimental data and theoretical constraints. However, the fact that such a pseudoscalar decays overwhelmingly into a bb¯ pair makes its identification at the Large Hadron Collider (LHC) a challenging task. After identifying the region of the flipped 2HDM parameter space yielding a light pseudoscalar, we identify a useful search channel in the process pp→AZ(Z*)→bb¯ℓ+ℓ−. A cut-based analysis, followed by one based on boosted decision trees, shows that the light-A scenario in flipped 2HDM should be detectable with rather high statistical significance at the high-luminosity LHC run, even after including systematic uncertainties. Furthermore, part of the parameter space, especially around mA=30–40  GeV, is amenable to detection at the discovery level within Run-2 itself.

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Phys. Rev. D 112, 075035– Published 17 October, 2025
  • Received 28 May 2025
  • Accepted 19 September 2025
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