On the Flavor Structure of Natural Composite Higgs Models & Top Flavor Violation

TL;DR

This paper analyzes the flavor structure of composite Higgs models, highlighting how flavor violation arises and predicting observable top flavor-changing processes like $t\to cZ$ at future colliders.

Contribution

It identifies the sources of flavor violation in minimal $SO(5)$ composite Higgs models and predicts large top flavor violation rates, providing testable signatures for upcoming experiments.

Findings

Large $t\to cZ$ branching ratio (~10^{-5}) is naturally expected.

Flavor violation effects are weakly correlated with fine-tuning levels.

Other flavor violations like $t\to ch$ are too small for near-future detection.

Abstract

We explore the up flavor structure of composite pseudo Nambu-Goldstone-boson Higgs models, where we focus on the flavor anarchic minimal $SO(5)$ case. We identify the different sources of flavor violation in this framework and emphasise the differences from the anarchic Randall-Sundrum scenario. In particular, the fact that the flavor symmetry does not commute with the symmetries that stabilize the Higgs potential may constrain the flavor structure of the theory. In addition, we consider the interplay between the fine tuning of the model and flavor violation. We find that generically the tuning of this class of models is worsen in the anarchic case due to the contributions from the additional fermion resonances. We show that, even in the presence of custodial symmetry, large top flavor violating rate are naturally expected. In particular, $t\to cZ$ branching ratio of order of $10^{-5}$ is generic for this class of models. Thus, this framework can be tested in the next run of the LHC as well as in other future colliders. We also find that the top flavor violation is weakly correlated with the increase amount of fine tuning. Finally, other related flavor violation effects, such as $t \to ch$ and in the $D$ system, are found to be too small to be observed by the current and near future colliders.