Interpreting the 650 GeV and 95 GeV Higgs anomalies in the N2HDM

Abstract

Recent experimental hints from the Large Hadron Collider (LHC) in di-photon and partially in the τ⁺τ⁻ final states suggest the possible existence of an additional Higgs boson with a mass around 95 GeV. Interestingly, these observations are consistent with earlier results from the Large Electron-Positron (LEP) collider, which pointed to an excess in b¯b final states within a similar mass range. Additionally, CMS has observed an excess in the γγb¯b final state, indicating a possible resonance near 650 GeV decaying into a pair of SM-like Higgs bosons or into a SM-like Higgs boson accompanied by a lighter scalar with mass near 95 GeV. In this work, we investigate whether these anomalies can be simultaneously explained within the Next-to-2-Higgs-DoubletModel (N2HDM), an extension of the Standard Model (SM) scalar sector featuring two complex Higgs doublets and an additional real singlet. Assuming the existence of a CP-even Higgs state compatible with the 95 GeV excesses (restricted to the γγ and b¯b channels), we analyse the Type-II and Type-Y Yukawa structures, taking the observed 650 GeV resonance to be a CP-even Higgs state. An extensive parameter scan is performed, incorporating the latest constraints from the properties of the observed 125 GeV Higgs boson, direct searches for additional Higgs states, flavour physics data and Electroweak Precision Observables (EWPOs). Our results show that a heavy CP-even Higgs resonance around 650 GeV, produced predominantly via gluon-gluon fusion and subsequently decaying into a 125 GeV Higgs boson together with another scalar at approximately 95 GeV, can be simultaneously accommodated within both the N2HDM Type-II and Type-Y frameworks at a significance level of 2σ. This interpretation leads to distinctive and testable predictions from the N2HDM for the ongoing LHC Run-3 and the forthcoming High-Luminosity LHC (HL-LHC) phase

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

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