Search for the rare decay KL→π0νν¯ at J-PARC KOTO experiment

Abstract

Abstract The KOTO experiment aims to study the CP-violating rare decay K L → π 0 ν ν ¯ at J-PARC. The analysis of the data set taken in 2016, 2017 and 2018 is reported. In order to reduce backgrounds and to improve the signal acceptance, a new barrel photon detector and a new trigger system were installed and new analysis techniques were developed. The K L yield was 7.1×1012. The single event sensitivity was estimated to be 6.9×10−10, which was improved by a factor of 2 compared to the data set taken in 2015. The number of background events was estimated to be 0.05 ± 0.02. Four candidate events were observed in the signal region, and their studies are on-going extensively to nd their sources.