The rare decay KL was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of (7.20±0.05stat±0.66syst)×10-10, three candidate events were observed in the signal region. After unveiling them, contaminations from K± and scattered KL decays were studied, and the total number of background events was estimated to be 1.22±0.26. We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of 4.9×10-9 on the branching fraction of KL→ π0ν ν at the 90% confidence level.
ASJC Scopus subject areas
- Physics and Astronomy(all)