Abstract
The rare decay was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of , three candidate events were observed in the signal region. After unveiling them, contaminations from and scattered decays were studied, and the total number of background events was estimated to be . We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of on the branching fraction of at the 90% confidence level.
- Received 15 December 2020
- Accepted 18 February 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.121801
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society