Anatomy of the real Higgs triplet model

Abstract

Abstract 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 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 ∆ ± $$ {m}_{\Delta ^{\pm }} $$ < 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)%.

Keywords

• Higgs Properties
• Multi-Higgs Models
• New Light Particles
• Other Weak Scale BSM Models