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

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 νh produced in νμ neutral-current-like neutrino interactions. If the νh exist, it would be also produced by the νμ beam from the CERN SPS in the neutrino beam line shielding. The νhʼs would penetrate the shielding and be observed through the νh→γν decay followed by the photon conversion into e+e− pair in the active target of the NOMAD detector. The νhʼs 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 νhʼs we set new constraints on νh properties and exclude part of the LSND/MiniBooNE νh 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 νh in future neutrino experiments.