Neutrino Masses from Non-minimal Gravitational Interactions of Massive Neutral Fermions

A new mechanism is proposed for generating neutrino masses radiatively through a non-minimal coupling to gravity of fermionic bilinears involving massive neutral fermions. Such coupling terms can arise in theories where the gravity sector is augmented by a scalar field. They necessarily violate the principle of equivalence, but such violations are not ruled out by present experiments. It is shown that the proposed mechanism is realised most convincingly in theories of the Randall- Sundrum type, where gravity couples strongly in the TeV range. The mechanism has the potential for solving both the solar and atmospheric neutrino problems. The smallness of neutrino masses in this scenario is due to the fact that the interaction of the massive neutral fermions arises entirely from higher-dimensional operators in the effective Lagrangian.