Search for Proton Decay into Muon plus Neutral Kaon in Super-Kamiokande   I, II, and III
  We have searched for proton into muon plus neutral kaon using data from a 91.7 kiloton-year exposure of Super-Kamiokande-I, a 49.2 kiloton-year exposure of Super-Kamiokande-II, and a 31.9 kiloton-year exposure of Super-Kamiokande-III. The number of candidate events in the data was consistent with the atmospheric neutrino background expectation and no evidence for proton decay in this mode was found. We set a partial lifetime lower limit of 1.6x10^33 years at the 90% confidence level. 
The Super-Kamiokande Collaboration: C.Regis, K.Abe, Y.Hayato, K.Iyogi,   J.Kameda, Y.Koshio, Ll.Marti, M.Miura, S.Moriyama, ...
hep-ex