Tau-sterile neutrino mixing in NOMAD

Abstract

For several years, the KARMEN experiment was reporting an anomalous signal which was interpreted as a possible existence of heavy sterile neutrinos. The NOMAD experiment has the capability to search for such an isosinglet neutrino. It is assumed that the (ν s ) couples to the ν τ produced in the SPS neutrino beam at CERN. Analysis of NOMAD data leads to a single candidate event, compatible with the background expectations. This allows a limit to be set for the first time on the mixing strength between sterile and tau neutrinos, in the mass range 10 to 190 MeV.