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Observation of the decay $K^+\to π^+ ν\barν$

Milind V. Diwan
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Abstract

We have observed 1 event consistent with the signature expected of the rare decay of a positive kaon to a positive pion and a neutrino anti-neutrino pair. In the examined momentum region of 211 to 230 MeV/c in the center of mass of the kaon we estimated the backgrounds to be about $0.08 \pm 0.03$ events. From this observation we estimate the branching ratio to be $4.2^{+9.7}_{-3.5} \times 10^{-10}$. In this presentation I will explain the experiment, and the analysis techniques. I will also discuss the expected improvements in the near future from the analysis of new data sets.

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Milind V. Diwan. 1999-03-14. Observation of the decay $K^+\to π^+ ν\barν$. https://arxiv.org/abs/hep-ex/9903026

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