Dimuons Produced by Antineutrinos

In a run with a predominantly $\overline{\ensuremath{\nu}}$ beam we have observed seven dimuon events which show clearly that dimuons are produced by $\overline{\ensuremath{\nu}}$ as well as by $\ensuremath{\nu}$. Using the signature of those events we tentatively identify twelve dimuon events from earlier runs as $\overline{\ensuremath{\nu}}$-induced. The characteristics of the total sample support the explanation that dimuons arise from new hadron production.