Search for weak neutral currents in semileptonic interactions

A search is made for weak neutral currents in semileptonic interactions. An experiment was performed in the neutrino beam of the Fermi National Accelerator Laboratory. While the existence of events without muons is strongly supported by the data, it is not yet possible to pin down their source. Several possibilities are considered which are consistent with the data. These include heavy lepton production, violation of muon number conservation, and the existence of weak neutral currents. For the case of heavy leptons it is shown that a mass of 3.1 +- 0.5 GeV/c2 and a small branching ratio into final states with muons would explain the observations. Under the assumption that weak neutral currents are the source, the space-time properties of the current are discussed in light of the variation of R with the energy transferred to the hadron system