Monophotons at Neutrino Experiments from Neutrino Polarizability

Nontrivial electromagnetic properties of neutrinos are an avenue to physics beyond the Standard Model. To this end, we investigate the power of monophoton signals at neutrino experiments to probe a higher-dimensional operator connecting neutrinos to SM photons dubbed, neutrino polarizability. A simplified scenario giving rise to this operator involves a new pseudo-scalar that couples to both neutrinos and photons, with clear implications for axion-like particle (ALP) and Majoron physics. By analyzing the photon energy spectrum and angular distributions, we find that NOMAD and MiniBooNE currently set the most stringent limits, while SBND and the DUNE near detector will soon provide significantly improved constraints.