Seesaw energy scale and the LSND anomaly

The most general, renormalizable Lagrangian that includes massive neutrinos contains “right-handed neutrino” Majorana masses of order $M$. While there are prejudices in favor of $M\gg M_{\mathrm{weak}}$, virtually nothing is known about the magnitude of $M$. I argue that the Liquid Scintillator Neutrino Detector (LSND) anomaly provides, currently, the only experimental hint: $M\sim 1\mathrm{eV}$. If this is the case, the LSND mixing angles are functions of the active neutrino masses and mixing and, remarkably, adequate fits to all data can be naturally obtained. I also discuss consequences of this “eV-seesaw” for supernova neutrino oscillations, tritium beta-decay, neutrinoless double-beta-decay, and cosmology.