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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>K</a:mi> <a:mi>L</a:mi> </a:msub> <a:mo stretchy="false">→</a:mo> <a:mn>3</a:mn> <a:msup> <a:mi>π</a:mi> <a:mn>0</a:mn> </a:msup> <a:mo stretchy="false">→</a:mo> <a:mn>6</a:mn> <a:mi>γ</a:mi> </a:math> data taken by the J-PARC KOTO experiment, to search for <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>K</e:mi> <e:mi>L</e:mi> </e:msub> <e:mo stretchy="false">→</e:mo> <e:mn>2</e:mn> <e:msup> <e:mi>π</e:mi> <e:mn>0</e:mn> </e:msup> <e:mi>a</e:mi> <e:mo stretchy="false">→</e:mo> <e:mn>6</e:mn> <e:mi>γ</e:mi> </e:math> . We also explore the power of KOTO <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>6</i:mn> <i:mi>γ</i:mi> </i:math> data to probe <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>K</k:mi> <k:mi>L</k:mi> </k:msub> <k:mo stretchy="false">→</k:mo> <k:mn>2</k:mn> <k:msup> <k:mi>π</k:mi> <k:mn>0</k:mn> </k:msup> <k:mi>a</k:mi> </k:math> for a broader range of ALP masses, incorporating displaced decays.