Study of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>K</mml:mi><mml:mi>L</mml:mi></mml:msub><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mi>ν</mml:mi><mml:mover accent="true"><mml:mi>ν</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover></mml:math> Decay at the J-PARC KOTO Experiment

The rare decay $K_L \!\to\! \pi^0 \nu \overline{\nu}$ was studied with the dataset taken at J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of $( 7.20 \pm 0.05_{\rm stat} 0.66_{\rm syst} ) \times 10^{-10}$, three candidate events were observed signal region. After unveiling them, contaminations from $K^{\pm}$ scattered $K_L$ decays studied, total number background estimated to be $1.22 0.26$. We conclude that is statistically consistent expectation. For this dataset, we set an upper limit $4.9 10^{-9}$ on branching fraction 90% confidence level.