Comprehensive ALP Searches in Meson Decays

TL;DR

This paper provides a comprehensive analysis of axion-like particles in meson decays, integrating effective field theory, UV models, and experimental data, including the Belle II anomaly, to enhance ALP search strategies.

Contribution

It introduces ALPaca, an open-source tool for ALP analysis, and combines theoretical and experimental approaches across energy scales for improved ALP constraints.

Findings

ALP constraints are strengthened through flavor observables.

The analysis includes non-perturbative QCD effects via chiral perturbation theory.

The study offers new insights into ALP signatures in meson decays.

Abstract

We present a comprehensive study of axion-like particles (ALPs) in meson decays, combining effective field theory and ultraviolet models within the open-source tool ALPaca. The analysis accounts for running and matching effects across energy scales, including non-perturbative QCD corrections via chiral perturbation theory. We discuss several benchmark models, both flavour-universal and non-universal, using the most up-to-date theoretical computations for ALP decays and branching ratios. Experimental signatures such as prompt, displaced, and invisible decays are included. A dedicated analysis of the Belle II anomaly in the decay $B^+ \to K^+ \nu \bar{\nu}$ is performed. Our results highlight the power of flavour observables in constraining ALPs and provide a versatile foundation for future searches.