Search for proton decay intoe++π0in the IMB-3 detector

Abstract

We report the results of a search for proton decay into $e^{+}+{\pi }^0$ in the 6800-ton IMB-3 water Čerenkov detector. During 376 days of live time no events consistent with this decay were found in the 3300 ton fiducial volume. From this observation we derive a limit on the partial lifetime to be $\frac{\tau }{B}>2.4\mathrm{}\times {10}^{32}$ yr (90% C.L.), which, combined with our previous result of 3.1×${10}^{32}$ yr, provides a limit of 5.5×${10}^{32}$ yr. The general features of the observed contained events are compatible with those expected from atmospheric neutrino interactions.