Dinucleon decay in the nucleus: A quark-model analysis

Baryon-number-violating decay of pairs of nucleons bound together in a nucleus is studied in the nonrelativistic quark model for a class of ordinary grand unified theories including minimal SU(5). Decay modes without mesons such as pp→pe+, and with pions such as pp→pe+π0, are considered. Both spectator and pole diagrams are included. The nonmesonic decay modes are negligible, but the effective p→e+π0 partial lifetime in oxygen (iron) is found to be roughly-equal25% (50%) longer than the free partial lifetime. Another possible lifetime increase related to an explanation of the European Muon Collaboration effect is discussed