We searched for the CP-violating rare decay of the neutral kaon, KL → π0ν ν, in data from the first 100 hours of physics running in 2013 of the J-PARC KOTO experiment. One candidate event was observed while 0.34 ± 0.16 background events were expected.We set an upper limit of 5.1 × 10-8 for the branching fraction at the 90% confidence level (C.L.). An upper limit of 3.7 × 10-8 at the 90% C.L. for the KL → π0X0 decay was also set for the first time, where X0 is an invisible particle with a mass of 135 MeV/c2.
ASJC Scopus subject areas
- Physics and Astronomy(all)