Sweeping the pion chimney for axion-like particles with KOTO

TL;DR

This paper proposes new methods to constrain axion-like particles in the pion chimney mass range using KOTO data, including recasting existing data and exploring displaced decay signatures.

Contribution

It introduces novel limits on prompt ALPs near the neutral pion mass by analyzing KOTO's 6-photon data and extends the search to displaced decays for a wider mass range.

Findings

New limits on prompt ALPs near the neutral pion mass.

Demonstrated the effectiveness of recasting KOTO data for ALP searches.

Explored the potential of KOTO data to detect displaced ALP decays.

Abstract

We demonstrate that novel limits on prompt axion-like particles (ALPs) in the hard-to-probe mass range near the neutral pion - the so-called pion chimney - may be obtained from recasting $K_L \to 3\pi^0 \to 6\gamma$ KOTO data to search for $K_L \to 2\pi^0 a \to 6\gamma$. We also explore the power of KOTO $6\gamma$ data to probe $K_L \to 2\pi^0a$ for a broader range of ALP masses, incorporating displaced decays.