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h→ϒγ decay: Smoking gun signature of a wrong-sign hbb¯ coupling

Aditya Batra1,2,*, Sanjoy Mandal3,†, and Rahul Srivastava1,‡

  • *Contact author: aditya.batra@tecnico.ulisboa.pt
  • †Contact author: smandal@kias.re.kr
  • ‡Contact author: rahul@iiserb.ac.in
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Phys. Rev. D 114, 055030 – Published 21 September, 2026

DOI: https://doi.org/10.1103/jndm-5wnt

Abstract

We perform a model-independent study of new physics effects in the Higgs decay h→ϒγ, focusing on scenarios that spoil the accidental cancellation between the direct and indirect amplitudes. After imposing all existing constraints from Higgs production and decay measurements, we find that a wrong-sign hbb¯ coupling is the only viable scenario capable of enhancing the h→ϒγ decay width by nearly 2 orders of magnitude. Therefore, an observation of a significantly enhanced h→ϒγ rate at the LHC or future colliders would provide unambiguous evidence for a wrong-sign hbb¯ coupling, directly pointing to the presence of an extended Higgs sector.

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Phys. Rev. D 114, 055030– Published 21 September, 2026
  • Received 27 January 2026
  • Accepted 13 August 2026
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