Sweeping the pion chimney for axion-like particles with KOTO

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 $K_L \to 3π^0 \to 6γ$ data taken by the J-PARC KOTO experiment, to search for $K_L \to 2π^0a \to 6γ$. We also explore the power of KOTO $6γ$ data to probe $K_L \to 2π^0a$ for a broader range of ALP masses, incorporating displaced decays.