Fundamental and composite scalars from extra dimensions

TL;DR

This paper explores a 4D effective theory with both fundamental and composite scalars originating from extra dimensions, analyzing its scalar spectrum and phenomenological implications, including flavor-changing neutral currents.

Contribution

It introduces a model combining fundamental and composite scalars from extra dimensions and analyzes its scalar spectrum and flavor-changing processes.

Findings

Acceptable parameter space is highly constrained.

Predicted large FCNC decay h -> tc with branching ratio ~10^{-3}.

Predicted large top FCNC decay t -> c + H with branching ratio ~10^{-4}.

Abstract

We discuss a scenario consisting of an effective 4D theory containing fundamental and composite fields. The strong dynamics sector responsible for the compositeness is assumed to be of extra dimensional origin. In the 4D effective theory the SM fermion and gauge fields are taken as fundamental fields. The scalar sector of the theory resembles a bosonic topcolor in the sense there are two scalar Higgs fields, a composite scalar field and a fundamental gauge-Higgs unification scalar. A detailed analysis of the scalar spectrum is presented in order to explore the parameter space consistent with experiment. It is found that, under the model assumptions, the acceptable parameter space is quite constrained. As a part of our phenomenological study of the model, we evaluate the branching ratio of the lightest Higgs boson and find that our model predicts a large FCNC mode h -> tc, which can be as large as O(10^{-3}). Similarly, a large BR for the top FCNC decay is obtained, namely B.R.(t -> c + H) \simeq 10^{-4}