We discuss muon and electron lepton-number nonconservation due to renormalization effects of the scalar-lepton mass matrix in spontaneously broken $N=1\mathrm{}$ supergravity theories. Differently from the case of massless or Dirac neutrinos, we find that if neutrinos are Majorana particles in a "seesaw" scheme the couplings photino-lepton-scalar-lepton lead to sizable rates for the processes $\mu \to e\gamma$ and $\mu +\mathrm{nucleus}\to e+\mathrm{nucleus}$. We discuss the constraints derived from the present experimental bounds.

• Received 5 June 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.961