Standard Model with a distorted Higgs sector and the enhanced Higgs diphoton decay rate

Abstract

We propose a theoretical justification for the anomalous Higgs couplings without extending the particle content of the Standard Model, but rather assuming different realization of the electroweak symmetry and the representation of the Higgs field. Namely, the electroweak symmetry in our model is non-linearly realised with the Higgs field residing in the singlet representation of the electroweak gauge group. Within this framework we identify the simplest scenario with CP-violating Higgs-top coupling which explains the enhanced rate of $h\to\gamma\gamma$, while the Higgs production cross section is unaffected. Remarkably, this can be achieved with a reduced strength of the Higgs-top Yukawa coupling, $| y_t|<| y^{\rm SM}_t|$, and, thus, the electroweak vacuum stability problem may also be resolved in our scenario without invoking new physics below the Planck scale. In addition, models with the distorted Higgs sector provide a new framework for potentially successful electroweak baryogenesis.