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 $K_L\to 3{\pi }^0\to 6\gamma$ data taken by the J-PARC KOTO experiment, 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 $K_L\to 2{\pi }^{0}a$ for a broader range of ALP masses, incorporating displaced decays.

Comments: 12 pages, 10 figures, updated to published version