Universal Constraints on Low-Energy Flavour Models

TL;DR

This paper identifies universal flavor-changing neutral current operators in low-energy flavor models, derives bounds on heavy messenger scales from experimental constraints, and highlights potential for discovering new physics in upcoming experiments.

Contribution

It introduces a universal framework for FCNC operators in flavor models and derives bounds on messenger scales considering different rotation assumptions.

Findings

Bounds on messenger scales vary with operators and rotations.

Upcoming experiments could reveal new physics in leptonic FCNC processes.

Leptonic processes like $ ightarrow e ightarrow e$ are promising discovery channels.

Abstract

It is pointed out that in a general class of flavour models one can identify certain universally present FCNC operators, induced by the exchange of heavy flavour messengers. Their coefficients depend on the rotation angles that connect flavour and fermion mass basis. The lower bounds on the messenger scale are derived using updated experimental constraints on the FCNC operators. The obtained bounds are different for different operators and in addition they depend on the chosen set of rotations. Given the sensitivity expected in the forthcoming experiments, the present analysis suggests interesting room for discovering new physics. As the highlights emerge the leptonic processes, $\mu\rightarrow e\gamma$, $\mu\rightarrow eee$ and $\mu\rightarrow e$ conversion in nuclei.