Dinucleon decay in the nucleus: A quark-model analysis.

Abstract

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\ensuremath{\rightarrow}${\mathrm{pe}}^{+}$, and with pions such as pp\ensuremath{\rightarrow}${\mathrm{pe}}^{+}$${\ensuremath{\pi}}^{0}$, are considered. Both spectator and pole diagrams are included. The nonmesonic decay modes are negligible, but the effective p\ensuremath{\rightarrow}${e}^{+}$${\ensuremath{\pi}}^{0}$ partial lifetime in oxygen (iron) is found to be \ensuremath{\approxeq}25% (50%) longer than the free partial lifetime. Another possible lifetime increase related to an explanation of the European Muon Collaboration effect is discussed.