Abstract
We propose a class of two Higgs doublet models where there are flavour changing neutral currents (FCNC) at tree level, but under control due to the introduction of a discrete symmetry in the full Lagrangian. It is shown that in this class of models, one can have simultaneously FCNC in the up and down sectors, in contrast to the situation encountered in the renormalisable and minimal flavour violating 2HDM models put forward by Branco et al. (Phys Lett B 380:119, 1996). The intensity of FCNC is analysed and it is shown that in this class of models one can respect all the strong constraints from experiment without unnatural fine-tuning. It is pointed out that the additional sources of flavour and CP violation are such that they can enhance significantly the generation of the Bbaryon asymmetry of the Universe, with respect to the standard model.
Highlights
S [7,8] can be implemented in a natural way through the introduction of a Z2 symmetry which leads to Natural
A very interesting approach to the control of flavour changing neutral currents (FCNC) is provided by Branco–Grimus–Lavoura (BGL) models [1], where there are FCNC at tree level but their flavour structure is controlled by the elements of the Cabibbo–Kobayashi–Maskawa (CKM) matrix V, with no other flavour parameters
We address ourselves to the question whether it is possible to generalise BGL models so that the new class of models, called generalised BGL, keep some of the interesting features of BGL models, like renormalisability, but allow for FCNC both in the up and the down sectors
Summary
At tree level which have to be suppressed in order to avoid violation of the stringent experimental bounds. The simplest way of avoiding FCNC in the scalar sector is by postulating that quarks of a given charge receive contributions to their mass only from one Higgs doublet. The general 2HDM contains FCNC, with their flavour structure parametrized by two complex matrices Nd , Nu [24] These matrices depend on a large number of parameters, in particular on ULd , ULu ,. Having Nd , Nu to depend only on V = ULu†ULd in a natural way looks like an impossible task This task is accomplished by BGL models, which were first constructed for the quark sector and generalized to.
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