Search

The production of the ϕ-meson in the reaction π− + p → ϕ + n has been studied using scintillation counters. The neutron was detected by a large-acceptance neutron detector and both its time of flight and its emission angle were measured to identify the missing mass. The decay mode ϕ→K+K− was detected using two scintillation counters in a simple coincidence arrangement. The total production cross-section of the ϕ-meson at 2.13 GeV/c turns out to be σ(π− + p → ϕ + n) = (24 ± 8) μb. This result confirms the depression factor, already observed for ϕ production in πN interactions, expected on the basis of the λ-quark spin conservation.

The flux of relativistic leptonic particles with charges ±e/3, ±2e/3, ±4e/3 in cosmic rays underground at 63 m w.e. was measured using a six-scintillation-counter telescope. The following upper limits were established: φ(±e/3)≤1.8·10−10 cm−2sr−1s−1, (90% confidence) φ(±2e/3)≤1.8·10−10 cm−2sr−1s−1, (90% confidence) φ(±4e/3)≤(1.1±1.8)·10−8 cm−2 sr−1 s−1, at threshold energies of (2.1±0.1) GeV, (8.5±0.6) GeV, (22±1) GeV respectively.

The results of a counter experiment on the branching ratioR=Γ(ω→neutrals)/Γ(ω→total) are presented. The masses of particles produced in the reaction π− + p → n + (missing mass) at 2.12 GeV/c were determined with an uncertainty of ±15 MeV by using counter techniques to measure the time of flight and emission angle of the neutrons. Veto counters around the hydrogen target selected neutral decay modes. The peak values of ω/background were 0.4 for the neutral mode and 0.55 for the total decay. Corrections to the experimental value are discussed. The value of the branching ratio was found to be (8.4±1.5)%. This result is compared with various theoretical predictions.