Dark origin of the quark flavor hierarchy and mixing

Abstract

We provide a dynamical mechanism for the generation of the Cabibbo-Kobayashi-Maskawa matrix in the context of a recently proposed model of flavor. The framework, based on the paradigm that Yukawa couplings are effective low energy couplings generated radiatively by dark sector interactions, is here extended to include a new scalar field which plays the role of a dark flavon. Being singlet under the Standard Model gauge group but charged under the U (1) symmetry of the dark sector, this particle sources new two-and three-loop diagrams that result in off-diagonal Yukawa interactions, thereby providing a simple explanation for the observed structure of the CKM matrix. By using an effective parametrization of these new loop contributions, we show that the CKM matrix elements can be correctly reproduced for perturbative values of the involved couplings. We outline the rich phenomenology predicted by the scenario and detail its implications for the LHC and future collider experiments.1

Vacuum stability with radiative Yukawa couplings

“…For instance, the use of nonperturbative dynamics in the dark sector easily allows exponentially spread dark fermions masses. The mechanism can therefore generate hierarchical SM Yukawa couplings that naturally fit the observed values, thereby solving the SM flavor puzzle [32][33][34]. Since in the present paper we are mainly concerned with the stability of the EW vacuum, which is not sensitive to the details of the flavour structure, we restrict ourselves to the generation of flavor-diagonal Yukawa couplings.…”

“…For instance, the mechanism is straightforwardly embedded in the scenarios of refs. [32][33][34] which were originally designed to solve the flavor hierarchy problem. In more detail, the tree-level Yukawa operators are forbidden by a new symmetry S: a discrete symmetry in ref.…”

“…[32] and a local SU(2) R extension of the SM gauge group in refs. [33,34]. In either case, the new symmetry is spontaneously broken by the vacuum expectation value v S of a dedicated scalar field which, thereby, allows for the emergence of the SM Yukawa operators.…”

“…A non-perturbative dynamics in the dark-sector, related to the U(1) D gauge symmetry, is responsible for the exponential spread of the dark fermion masses and, therefore, for the observed hierarchy of the SM Yukawa couplings [35]. The same framework also allows for the radiative origin of flavor mixing, modelled in the Cabibbo-Kobayashi-Maskawa matrix [34].…”

“…We conclude the section with a brief review of the phenomenological implications of the framework, based on the works of refs. [34,[37][38][39][40][41][42][43][44].…”