Supergravity can reconcile dark matter with lepton number violating neutrino masses

Supersymmetry offers a cold dark matter candidate, provided that lepton number is not violated by an odd number of units. On the other hand, lepton number violation by even (two) units gives us an attractive mechanism of neutrino mass generation. Here we offer an explanation of this, in a supergravity framework underlying a supersymmetric scenario, the essential feature being particles carrying lepton numbers, which interact only gravitationally with all other known particles. It is shown that one can have the right amount of ΔL=2 effect giving rise to neutrino masses, whereas the lifetime for ΔL=1 decays of the lightest supersymmetric particle can be prolonged beyond the present age of the Universe