Minimal Flavor Violation with Axion-like Particles

TL;DR

This paper analyzes flavor-changing processes involving axion-like particles (ALPs), focusing on minimal models where flavor violation arises radiatively, and discusses implications for UV completions including string theory scenarios.

Contribution

It introduces a minimal ALP model with flavor-conserving tree-level couplings, where flavor violation is generated radiatively, and explores UV completions and string theory implications.

Findings

Radiatively generated flavor-changing ALP couplings can be suppressed in UV-complete models.

Implications for string-theoretic ALPs from higher-dimensional gauge fields.

Minimal flavor violation scenario with loop-induced flavor-changing processes.

Abstract

We revisit the flavor-changing processes involving an axion-like particle (ALP) in the context of generic ALP effective lagrangian with a discussion of possible UV completions providing the origin of the relevant bare ALP couplings. We focus on the minimal scenario that ALP has flavor-conserving couplings at tree level, and the leading flavor-changing couplings arise from the loops involving the Yukawa couplings of the Standard Model fermions. We note that such radiatively generated flavor-changing ALP couplings can be easily suppressed in field theoretic ALP models with sensible UV completion. We discuss also the implication of our result for string theoretic ALP originating from higher-dimensional $p$-form gauge fields, for instance for ALP in large volume string compactification scenario.