Global constraints on a heavy neutrino

Abstract

We estimate constraints on the existence of a heavy, mostly sterile neutrino with mass between 10 eV and 1 TeV. We improve upon previous analyses by performing a global combination and expanding the experimental inputs to simultaneously include tests for lepton universality, lepton-flavor-violating processes, electroweak precision data, dipole moments, and neutrinoless double beta decay. Assuming the heavy neutrino and its decay products are invisible to detection, we further include, in a self-consistent manner, constraints from direct kinematic searches, the kinematics of muon decay, cosmology, and neutrino oscillations, in order to estimate constraints on the values of $|{U}_{e4}{|}^{2}$, $|{U}_{\ensuremath{\mu}4}{|}^{2}$, and $|{U}_{\ensuremath{\tau}4}{|}^{2}$.