Upper Limits to<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>μ</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>−</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Oscillation and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>ν</mml:mi></mml:mrow><mml:mrow><mml:mi>μ</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mo>−</mml:mo><mml:mi>τ</mml:mi></mml:math>Coupling

A search for $\ensuremath{\tau}$ lepton production in a sample of 1241 neutrino interactions with use of a hybrid emulsion spectrometer in the Fermilab wide-band neutrino beam is reported. No such events are seen and an upper limit to the ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{-}\ensuremath{\tau}$ coupling of 0.63% (90% C.L.) is set. For ${\ensuremath{\nu}}_{\ensuremath{\mu}}\ensuremath{-}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ oscillations this sets a limit of $|{{m}_{{\ensuremath{\nu}}_{\ensuremath{\mu}}}}^{2}\ensuremath{-}{{m}_{{\ensuremath{\nu}}_{\ensuremath{\tau}}}}^{2}|&lt;3.0$ ${\mathrm{eV}}^{2}$ (90% C.L.) for maximum mixing.