Clockwork Neutrinos

Abstract

Clockwork (CW) mechanism can explain the smallness of neutrino masses without introducing unnaturally small input parameters. In this paper we study the simplest CW neutrino model, the "uniform" clockwork, as well as a broader class of "generalized" clockwork models. We derive constraints on such models from lepton-flavor violating processes, as well as precision electroweak fits. These constraints allow excited CW neutrino states with masses of order 100 GeV -- 1 TeV, within reach of the LHC and proposed lepton colliders, as long as the input neutrino Yukawa coupling is of order $10^{-1}-10^{-2}$. We study collider phenomenology of these models. At the LHC, models with light ($\sim 100$~GeV) CW neutrinos can be discovered using the $3\ell+$ MET signature. Lepton colliders will be able to discover the CW neutrinos as long as they are within their kinematic range.