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Indications for new scalar resonances at the LHC and a possible interpretation

Anirban Kundu*

Poulami Mondal†

Gilbert Moultaka‡

  • *Contact author: akphy@caluniv.ac.in
  • †Contact author: poulami.mondal@tifr.res.in
  • ‡Contact author: gilbert.moultaka@umontpellier.fr
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Phys. Rev. D 113, 055053 – Published 31 March, 2026

DOI: https://doi.org/10.1103/pfxp-dxt4

Abstract

Over the last few years, the CMS and ATLAS Collaborations at the Large Hadron Collider (LHC) have reported excesses that could hint at several new scalar resonances. Although none of them have touched the discovery level, at least two of them, at about 95 and 650 GeV, have been indicated by more than one experiment and have reached statistical significance worthy of a serious investigation. Conservatively using only the numbers given by the experimental collaborations, we find combined global significances around 3σ and 4σ, respectively, for the 95 and 650 GeV putative resonances. There are some more, like the one at 320 GeV, which have also been hinted at. We show that the data on only the 650 GeV resonance, assuming they stand the test of time, predict the existence of a doubly charged scalar and make the more common extensions of the scalar sector like those by gauge singlet scalars, the two-Higgs doublet models, or the Georgi-Machacek model highly disfavored. We provide the readers with a minimalistic model that may possibly explain all the indications. Such a model can also accommodate the hints of a singly charged scalar at about 375 GeV and a doubly charged scalar at about 450 GeV, as found by both the major LHC collaborations, the combined global significance for each of them being above 2.5σ. We show that even the scant data, with large error bars, have the potential to strongly constrain our model containing four scalar multiplets, which makes the model easily testable and falsifiable. Our analysis comes with the obvious caveat that the allowed parameter space that we find depends on the available data on all the new resonances and may change in future. One may also note that this is an exploratory exercise that illustrates the difficulties when it comes to fitting several resonances simultaneously, even for next-to-minimal extensions of the Standard Model.

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Phys. Rev. D 113, 055053– Published 31 March, 2026
  • Received 30 November 2024
  • Accepted 11 February 2026
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