Abstract

We analyse various flavour-changing processes like $$t\rightarrow hu,hc$$ , $$h\rightarrow \tau e,\tau \mu $$ as well as hadronic decays $$h\rightarrow bs,bd$$ , in the framework of a class of two Higgs doublet models where there are flavour-changing neutral scalar currents at tree level. These models have the remarkable feature of having these flavour-violating couplings entirely determined by the CKM and PMNS matrices as well as $$\tan \beta $$ . The flavour structure of these scalar currents results from a symmetry of the Lagrangian and therefore it is natural and stable under the renormalisation group. We show that in some of the models the rates of the above flavour-changing processes can reach the discovery level at the LHC at 13 TeV even taking into account the stringent bounds on low energy processes, in particular $$\mu \rightarrow e\gamma $$ .

Highlights

  • In this paper, we investigate the allowed strength of Higgs Flavour Violating Neutral Couplings (HFVNCs) in the framework of a class of 2HDM, denoted BGL models, first proposed for the quark sector [6], generalised in [7] and extended to the leptonic sector [8]

  • We call up-type BGL models those with HFVNCs in the down sector, coming from the symmetry given by Eq (2) and we identify each one of the three implementations by u type, c type or t type depending on the value of the index j, respectively 1, 2 or 3

  • We analyse flavour-changing scalar couplings in the framework of a class of two Higgs Doublet models where these couplings arise at tree level, but with their flavour structure entirely determined by the Cabibbo– Kobayashi–Maskawa (CKM) and Pontecorvo– Maki–Nakagawa–Sakata (PMNS) matrices

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Summary

Introduction

We investigate the allowed strength of HFVNCs in the framework of a class of 2HDM, denoted BGL models, first proposed for the quark sector [6], generalised in [7] and extended to the leptonic sector [8]. The constraints derived from low energy phenomenology have to be considered: both those obtained in [46] and those new due to the presence of H0–R0 mixing Processes such as h → bs and h → bd are probably not within reach of the LHC but become important for the physics of the future Linear Collider. The paper contains two appendices, in Appendix A, we explain how the relevant Higgs experimental data has been incorporated into the analysis, and in Appendix B.3, we give details relative to the low energy flavour constraint μ → eγ

Main features of BGL models
Flavour-changing decays of top quarks
Flavour-changing Higgs decays
Correlations among observables
Conclusions
A Higgs signals
B Constraints
Perturbative unitarity
Mesons mixings
X and zX
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