In this article, we examine the Standard Model extended by a Y = 0 real Higgs triplet, the ∆SM. It contains a CP-even neutral Higgs (∆0) and two charged Higgs bosons (∆±), which are quasi-degenerate in mass. We first study the theoretical constraints from vacuum stability and perturbative unitarity and then calculate the Higgs decays, including the loop-induced modes such as di-photons (γγ) and Zγ. In the limit of a small mixing between the SM Higgs and ∆0, the latter decays dominantly to WW and can have a sizable branching ratio to di-photon. The model predicts a positive definite shift in the W mass, which is compatible with the current global electroweak fit. At the Large Hadron Collider, it leads to a (i) stau-like signature from pp → ∆+∆− → <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25877_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="59" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msup> <mi>τ</mi> <mo>+</mo> </msup> <msup> <mi>τ</mi> <mo>−</mo> </msup> <mi>ν</mi> <mover accent="true"> <mi>ν</mi> <mo stretchy="true">¯</mo> </mover> </math></EquationSource> <EquationSource Format="TEX">$ {\tau}^{+}{\tau}^{-}\nu \overline{\nu} $</EquationSource> </InlineEquation>, (ii) multi-lepton final states from pp → γ → ∆+∆− → W+W−ZZ and pp → W → ∆±∆0 → W±ZW+W− as well as (iii) associated di-photon production from pp → W* → ∆±(∆0 → γγ). Concerning (i), the reinterpretation of the recent supersymmetric tau partner search by ATLAS and CMS excludes <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13130_2025_25877_Article_IEq2.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="MATHML"><math display="inline"> <msub> <mi>m</mi> <msup> <mtext>∆</mtext> <mo>±</mo> </msup> </msub> </math></EquationSource> <EquationSource Format="TEX">$ {m}_{\Delta ^{\pm }} $</EquationSource> </InlineEquation> < 110 GeV at 95% CL. From (ii), some of the signal regions of multi-lepton searches lead to bounds close to the predicted cross-section, but electroweak scale masses are still allowed. For (iii), the recast of the associated di-photon searches by ATLAS and a combined log-likelihood fit of signal and background to data find that out of the 25 signal regions, 10 provide relevant limits on Br(∆0 → γγ) at the per cent level. Interestingly, 6 signal regions show weaker than expected limits at around 152 GeV, leading to a preference for a non-zero di-photon branching ratio of about (0.7±0.2)%.

Anatomy of the real Higgs triplet model

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2025年4月1日

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Saiyad Ashanujjaman,
Sumit Banik,
Guglielmo Coloretti,
Andreas Crivellin,
Siddharth P. Maharathy,
Bruce Mellado

摘要

In this article, we examine the Standard Model extended by a Y = 0 real Higgs triplet, the ∆SM. It contains a CP-even neutral Higgs (∆⁰) and two charged Higgs bosons (∆^±), which are quasi-degenerate in mass. We first study the theoretical constraints from vacuum stability and perturbative unitarity and then calculate the Higgs decays, including the loop-induced modes such as di-photons (γγ) and Zγ. In the limit of a small mixing between the SM Higgs and ∆⁰, the latter decays dominantly to WW and can have a sizable branching ratio to di-photon. The model predicts a positive definite shift in the W mass, which is compatible with the current global electroweak fit. At the Large Hadron Collider, it leads to a (i) stau-like signature from pp → ∆⁺∆⁻ → $τ^{+} τ^{-} ν \bar{ν}$ $ {\tau}^{+}{\tau}^{-}\nu \overline{\nu} $ , (ii) multi-lepton final states from pp → γ^* → ∆⁺∆⁻ → W⁺W⁻ZZ and pp → W^* → ∆^±∆⁰ → W^±ZW⁺W⁻ as well as (iii) associated di-photon production from pp → W^* → ∆^±(∆⁰ → γγ). Concerning (i), the reinterpretation of the recent supersymmetric tau partner search by ATLAS and CMS excludes $m_{∆^{\pm}}$ $ {m}_{\Delta ^{\pm }} $ < 110 GeV at 95% CL. From (ii), some of the signal regions of multi-lepton searches lead to bounds close to the predicted cross-section, but electroweak scale masses are still allowed. For (iii), the recast of the associated di-photon searches by ATLAS and a combined log-likelihood fit of signal and background to data find that out of the 25 signal regions, 10 provide relevant limits on Br(∆⁰ → γγ) at the per cent level. Interestingly, 6 signal regions show weaker than expected limits at around 152 GeV, leading to a preference for a non-zero di-photon branching ratio of about (0.7±0.2)%.