New limits on radiative sterile neutrino decays from a search for single photons in neutrino interactions

TL;DR

This paper sets new constraints on the properties of hypothetical heavy sterile neutrinos by analyzing single photon events in neutrino interactions, refining previous bounds and highlighting open parameter space for future searches.

Contribution

The study uses NOMAD and CHORUS data to improve limits on sterile neutrino decay parameters, excluding parts of the LSND/MiniBooNE favored regions.

Findings

New bounds on sterile neutrino properties established.

Part of the parameter space remains accessible for future experiments.

Constraints exclude some LSND/MiniBooNE interpretations.

Abstract

It has been recently shown that excess events observed by the LSND and MiniBooNE neutrino experiments could be interpreted as a signal from the radiative decay of a heavy sterile neutrino \nu_h produced in \nu_\mu neutral current-like interactions. If the \nu_h exist, it would be also produced by the \nu_\mu beam from the CERN SPS in the neutrino beam line shielding. The \nu_h's would penetrate the shielding and be observed through the decay \nu_h -> \nu \gamma, followed by the photon conversion into e+e- pair in the active target of the NOMAD detector. The \nu_h's could be also produced in the iron of the magnetic spectrometer of the CHORUS detector, located just in front of NOMAD. Considering these two sources of \nu_h's we set new constraints on \nu_h properties and exclude part of the LSND/MiniBooNE \nu_h parameter space using bounds on single photons production in neutrino reactions recently reported by the NOMAD collaboration. We find that broad bands in the parameter space are still open for more sensitive searches for the \nu_h in future neutrino experiments.