Neutral Currents in High-Energy Neutrino Collisions: An Experimental Search

A search for events with no final-state muon, as expected in the neutral-current interactions ${{ν}}_{{μ}}({{{ν}}}_{{μ}})+N{→}{{ν}}_{{μ}}({{{ν}}}_{{μ}})+hadrons$, has been carried out by using the California Institute of Technology-Fermilab neutrino detector and narrow-band neutrino beam. A clear signal of events with no apparent final-state muon has been observed. Furthermore, missing energy in the final state for these events provides strong evidence for the existence of a final-state ν.