Opposite-sign dilepton production inνμinteractions

We report on a high-statistics bubble-chamber experiment using the Fermilab 15-ft bubble chamber filled with a heavy neon/hydrogen mixture exposed to a wide-band neutrino beam. In a sample of 106 000 ${\nu }_{\mu }$ &>0.3 GeV/c) and a negative muon were observed. After corrections, the rate for opposite-sign dilepton production for ${\nu }_{\mu }$ charged-current events is (0.52±0.09)%. The $E_{\nu }$ dependence of this rate from threshold to ≊200 GeV is presented. The kinematic distributions and strange-particle content of the dilepton events are consistent with those expected from charm-particle production in neutrino interactions. A total of 58 neutral strange particles (Λ→p${\pi }^{\mathrm{-}}$, $K_S^0$→${\pi }^{+}$ ${\pi }^{\mathrm{-}}$) are observed in these events, where less than 16 are expected from conventional charged-current interactions. The presence of a significant excess of Λ’s is evidence for substantial charmed-baryon production.