Search

In an exposure of the Fermilab 15-foot neon-hydrogen bubble chamber to a quadrupole triplet neutrino beam, 49 ..mu../sup -/e/sup +/ and 14 ..mu../sup +/e/sup -/ events with e/sup + -/ momenta greater than 0.3 GeV/c have been observed, yielding ..mu..e rates per charged-current event of (0.73 +- 0.11)% and (1.1 +- 0.3)%, respectively. The ..mu../sup -/e/sup +/ rate shows no strong energy dependence in the range from 30 to 300 GeV. The 18 neutral strange particles observed in the 63 events contain 14 K/sup 0//sub S/, 2 ..lambda.., and 2 ..lambda../K/sup 0//sub S/ ambiguities, suggesting that the events are predominantly D-meson production and decay and that the ..lambda../sup +//sub c/..--> lambda..eX branching ratio is very small. The corrected numbers of neutral strange particles per ..mu../sup -/e/sup +/ and ..mu../sup +/e/sup -/ event are 1.2 +- 0.3 and 0.6/sup +0.6//sub -0.3/, respectively. Properties of the events, including strange-particle production, are compared to ..mu../sup - +/..mu../sup + -/ events in the same experiment and to a charm production and decay model, and good agreement is found, apart from a possible enhancement at approx.5--6 GeV/c/sup 2/ in the mass of the system recoiling against the ..mu../sup +/ in ..mu../sup +/e/sup -/ (and ..mu../supmore » +/..mu../sup -/) events. As reported previously, four events show short-lived-particle decays, and D-meson lifetime estimates are reevaluated using the final event sample. One ..mu../sup +/e/sup +/ and three ..mu../sup -/e/sup -/ events were observed. The ..mu../sup -/e/sup -/ events are consistent with background and lead to a ..mu../sup -/e/sup -//..mu../sup -/e/sup +/ ratio of less than 0.07 (90% confidence level) for e/sup + -/ momenta above 0.8 GeV/c. Five candidates for dilepton production by electron neutrinos and antineutrinos in the beam are consistent with approximately 1% rates. No good three-lepton candidates were found, and one, previously reported, four-lepton candidate was found.« less

We report observation of a neutrino (antineutrino)-induced event with two electrons, one positron, one positively charged muon, a neutral K meson, and seven gammas in an experiment performed in the FNAL 15-ft. bubble chamber with a 47% atomic mixture of neon in hydrogen. Estimated experimental electron backgrounds are ∼10 −4 per track. At present we have no plausible interpretation of this event.

Examination of a sample of 89 high-energy, neutrino-induced dilepton events produced in the Fermilab 15 ft bubble chamber has resulted in the direct observation of the production and visible semi-leptonic decay of short-lived particles. One charged decay, two neutral decays, and one decay candidate of undetermined charge are found. Assuming these events and the remaining dilepton signal result from D meson decays, we obtain τ D + = 2.5 −1.5 +3.5 × 10 −13 s and τ D 0 = 3.5 −1.7 +3.5 × 10 −13 s, using a maximum likelihood analysis.