Experimental Limits on the Nucleon Lifetime for Two- and Three-Body Decay Modes

Abstract

Lower limits in the range of ${10}^{31}$ to ${10}^{32}$ yr for the partial lifetimes of a number of nucleon decay modes are obtained from a 204-live-day exposure in an 8-ktonne water Cherenkov detector (3.3 ktonne in the fiducial volume). During this period 169 contained events were observed at a rate and with characteristics consistent with expected backgrounds from atomospheric $\nu$ interactions. Nine of the contained events are compatible with either a $\nu$ interaction or nucleon decay into a number of non-$\nu$ modes.