Radiative decay of heavy neutrinos at MiniBooNE and MicroBooNE

Abstract

The MiniBooNE experiment reported results from the analysis of $\nu_e$ and $\overline{\nu}_e$ appearance searches, which showed an excess of signal-like events at low reconstructed neutrino energies with respect to the expected background. A proposed explanation for this anomaly is based on the existence of a heavy ($\sim 50$~MeV) sterile neutrino. These $\nu_h$ would be produced by $\nu_\mu$ electromagnetic and neutral current interactions. A fraction of them decays radiatively inside the detector. The emitted photon is misidentified as an electron or positron in MiniBooNE. We have investigated the $\nu_h$ production by coherent and incoherent electroweak interactions at the MiniBooNE and MicroBooNE targets, CH$_2$ and Ar, respectively. Studying the $\nu_h$ propagation inside the detector, we obtain the energy and angular distributions of emitted photons for a choice of model parameters. The distinctive shape and total number of photon events from this mechanism at MicroBooNE makes its experimental investigation possible.