Gauge-Theory Heavy Muons: An Experimental Search

We have observed 1522 neutrino events with a ${\mu }^{-}$ secondary and 8 events with a ${\mu }^{+}$ secondary from a beam consisting mostly of neutrinos. The ${\mu }^{+}$ events are consistent in number and kinematic properties with beam contamination by ${\overline{\nu }}_{\mu }$. This experiment sees no evidence for production of heavy positively charged leptons. Assuming a coupling constant equal to the universal Fermi constant and a branching ratio to muons $B=0.3\mathrm{}$, our 90% confidence lower limit corresponds to $M_{Y^{+}}\gtrsim 8.4$ ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$.