Reexamining the search for light ALPs at flavor and forward accelerator experiments

TL;DR

This paper reevaluates the sensitivity of forward accelerator experiments and flavor constraints to light axion-like particles, incorporating recent decay measurements and comprehensive decay mode analyses to improve detection prospects.

Contribution

It provides a detailed analysis of flavor constraints and experimental sensitivities for light ALPs, considering both flavor-violating and flavor-conserving couplings with recent decay data.

Findings

Heavy meson decays and forward experiments are complementary in probing light ALPs.

Recent decay measurements significantly tighten bounds on ALP-quark flavor violation.

The interplay of different ALP couplings affects detection strategies.

Abstract

The axion-like particle (ALP) is a well-motivated extension of the Standard Model. In this work, we revisit the sensitivity of forward accelerator experiments to light long-lived ALPs, and analyze flavor constraints. Our analysis incorporates recent measurements of the rare decays $B\to K + X$ and $K\to \pi +X$, which place stringent bounds on quark flavor violation of a light ALP. We consider the complete list of hadronic modes in the calculation of the ALP decay rate and exclusive production channels based on recent improvements. The analysis includes the discussion of tree-level quark flavor-violating couplings in addition to a universal flavor-conserving ALP coupling to fermions and the electroweak ALP couplings. Our results demonstrate the complementarity of heavy meson decays and forward accelerator facilities in probing light ALPs. The interplay between two ALP couplings is also investigated.