Minimal violation of flavour and custodial symmetries in a vectophobic Two-Higgs-Doublet-Model

Elvira Cerveró,Jean-Marc Gérard

doi:10.1016/j.physletb.2012.05.010

Elvira Cerveró, Jean-Marc Gérard

Open Access

https://doi.org/10.1016/j.physletb.2012.05.010

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Journal: Physics Letters B	Publication Date: May 7, 2012
Citations: 53	License type: cc-by

Affiliation: Université Catholique de Louvain

Abstract

Tree-level accidental symmetries are known to play a fundamental role in the phenomenology of the Standard Model (SM) for electroweak interactions. So far, no significant deviations from the theory have been observed in precision, flavour and collider physics. Consequently, these global symmetries are expected to remain quite efficient in any attempt beyond the SM. Yet, they do not forbid rather unorthodox phenomena within the reach of current LHC experiments. This is illustrated with a vectophobic Two-Higgs-Doublet-Model (2HDM) where effects of a light, flavour-violating and custodian (pseudo)scalar might be observed in the Bs→μ+μ− decay rate and in the diphoton invariant mass spectrum at around 125 GeV.

Highlights

Baryon number conservation, invoked [1] to explain the striking stability of the proton against p → e+γ, played a crucial role in the building of the quark model and turned out to be a tree-level accidental symmetry of the SM
The so-called custodial symmetry is an accidental one arising from the Higgs potential of the SM
If we impose a custodial symmetry on the 2HDM potential, the physical states can be naturally classified in triplet and singlet irreducible representations of the unbroken SU (2)L+R, namely

Summary

Introduction

Baryon number conservation, invoked [1] to explain the striking stability of the proton against p → e+γ , played a crucial role in the building of the quark model and turned out to be a tree-level accidental symmetry of the SM. Once split into distinct sectors, the SU(2)L × U (1)Y gauge-invariant SM Lagrangian has progressively revealed other accidental global symmetries that are quite useful for our understanding of electroweak processes among the three up and down quarks. The so-called custodial symmetry is an accidental one arising from the Higgs potential of the SM. It has been identified [2] as the responsible for the amazing success of the tree-level mass relation ρ≡

Z cos2

Custodial symmetry

Flavour symmetries

Findings

Conclusion