Baryon-number-violating (ΔB=2) processes are predicted by a variety of grand (or partially) unified theories of the fundamental interactions. In this paper we explore the double proton decay inside nuclei. We calculate the width Γ for the associated exotic nuclear decay and, by exploiting the experimental data on nuclear stability, we are able to set an upper bound on the coupling constant K of the corresponding effective Lagrangian. This, in turn, can be converted into a lower bound for the time of oscillation of hydrogen into antihydrogen. The latter turns out to be much more stringent than the one inferred from astrophysical observations.

• Received 13 June 1985

DOI:https://doi.org/10.1103/PhysRevC.32.1722