  We propose a way of protecting a Dirac fermion interacting with a scalar
field from acquiring a mass from the vacuum. It is obtained through an
implementation of translational symmetry when the theory is formulated with a
momentum cutoff, which forbids the usual Yukawa term. We consider that this
mechanism can help to understand the smallness of neutrino masses without a
tuning of the Yukawa coupling. The prohibition of the Yukawa term for the
neutrino forbids at the same time a gauge coupling between the right-handed
electron and neutrino. We prove that this mechanism can be implemented on the
lattice.
