U(1)' mediated decays of heavy sterile neutrinos in MiniBooNE

Abstract

The MiniBooNE low-energy excess is a longstanding problem which has received further confirmation recently with a reanalysis using newly collected data, with the anomaly now at the $4.8σ$ level. In this letter we propose a novel explanation which advocates a low-energy sector containing $Z^\prime$ bosons with GeV-scale masses and sterile neutrinos with masses around $100$-$500$ MeV. We show that this scenario can provide an excellent spectral agreement with the MiniBooNE low-energy excess in the form of $Z^\prime$-mediated neutral current production of heavy sterile states, a fraction of whose subsequent decay to $e^+e^-$ pairs are misidentified as single electron-like electromagnetic showers. Our model inscribes itself in the broad class of models in which sterile neutrinos are charged under novel interactions, allowing new couplings to hidden-sector physics. Alongside the electron-like MiniBooNE signature this model also predicts a novel, low-background, signal in LArTPC detectors such as MicroBooNE consisting of two distinguishable electron-like electromagnetic showers originating from a single vertex with no associated hadronic activity.