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arXiv · 2611.08514

The Koto II experiment

Silvia Martellotti
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Abstract

$K_L \rightarrow π^0ν\barν$ is a golden mode for flavour physics: it is highly suppressed in the Standard Model, with a predicted branching ratio of $3 \times 10^{-11}$ and a theoretical uncertainty of just 2\%, and is therefore extremely sensitive to new physics. The KOTO experiment at J-PARC is searching for this decay. Using the data taken in 2021, it has set the most stringent upper limit to date of $2.2 \times 10^{-9}$ on the branching ratio at 90\% C.L. We present KOTO II, a next-generation experiment at J-PARC proposed in 2024, which aims to measure the $K_L \rightarrow π^0ν\barν$ branching ratio with a sensitivity below $10^{-12}$ in the 2030s.

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Silvia Martellotti. 2026-10-19. The Koto II experiment. https://arxiv.org/abs/2611.08514

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