Light from the Neutrinos

Neutrinos are one of the most abundant of all known particles in the Universe, but yet the least understood ones. In the Standard Model, neutrinos are massless and interact only via the weak force. However, the discovery of neutrino oscillations implies that neutrinos are massive and mixed. Therefore, the Standard Model must be extended to account for the tiny neutrino masses. In these extensions, neutrinos also acquire electromagnetic properties through quantum loops effects. Hence, the theoretical and experimental investigation of neutrino electromagnetic interactions can serve as a powerful tool in searching for the fundamental theory behind the neutrino mass generation mechanism. We show that the models that induce neutrino magnetic moments while maintaining their small masses naturally also predict observable shifts in the charged lepton anomalous magnetic moment. This shift is of the right magnitude to be consistent with the Brookhaven measurement as well as the recent Fermilab measurement of the muon $g-2$. This points out the direct correlation between the magnetic moment of SM charged lepton and neutral lepton (neutrino) by showing that the measurement of muon $g-2$ by the Fermilab experiment can be an in-direct and novel test of the neutrino magnetic-moment hypothesis,  which can be as sensitive as other ongoing-neutrino/dark matter experiments. Such a correlation between muon $g-2$ and the neutrino magnetic moment is generic in models employing leptonic family symmetry to explain a naturally large neutrino magnetic moment. This talk will be based on results obtained with K.S. Babu and Manfred Lindner and presented in hep-ph 2007.04291 and 2104.03291.