Probing axionlike particles near the neutral pion mass with KOTO data

We demonstrate that novel limits on prompt axionlike 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 → 3 π 0 → 6 γ data taken by the J-PARC KOTO experiment, to search for K L → 2 π 0 a → 6 γ . We also explore the power of KOTO 6 γ data to probe K L → 2 π 0 a for a broader range of ALP masses, incorporating displaced decays.