  We discuss the prospects for detecting right-handed neutrinos which are
introduced in the see-saw mechanism at future colliders. This requires a very
accurate cancellation between contributions from different right-handed
neutrinos to the light neutrino mass matrix. We search for possible symmetries
behind this cancellation and find that they have to include lepton number
conservation. Light neutrino masses can be generated as a result of small
symmetry-breaking perturbations. The impact of these perturbations on LHC
physics is negligible, so that the mechanism of neutrino mass generation and
LHC physics are decoupled in general. In constrained cases, accelerator
observables and neutrino masses and mixings can be correlated.
