Search

32 pp. (1977).

46 pp. (1978).

21 pp. (1978)., Decays of the heavy lepton τ have now been observed in e+e− ‐ collisions at the energy of the ψ′‐resonace, which results in an improved mass determination Mτ=1.807±0.020 GeV. For the τ‐life‐time a new upper limit of ττ?3.5⋅10−12 sec. is given. The evidence for the decay τ→νπρ has been strengthened, and the πρ‐system is found to be in an S‐wave state with JP=1+, proving the axial vector component in the leptonic coupling of the τ to hadrons. The branching ratio is given with BR(τ−→νπ−ρ0) =0.050±0.015. The total hadronic cross section agrees within errors with the quarksum rule including QCD‐corrections. The production and decay distributions of the decay J/ψ→f0γ have been measured and found to agree well with a QCD calculation based on the exchange of two gluons.

(1978). doi:10.1016/0370-2693(78)90183-1, The cross sections for e + e − → e + ( μ + + non showering track + any photons have been measured for cm energies between 3.1 GeV and 5.2 GeV. We observe τ -pair production below the thresholdfor charm production and determine the τ mass to be 1.807 ± 0.020 GeV from a fit to the energy dependence of the cross section. The ration of the leptonic branching ratios B μ / B e = 0.92 ± 0.32 is consistent with eμ-universality. The following branching ratios are determined for a V-A coupling: B(τ → ν τ e ν ) = B(τ → ν τ μ ν ) = 0.182 + 0.028 . B ( τ → ν τ + charged hadron + any photons) = 0.29 ± 0.11, B ( τ → ν τ + three or more charged hadrons + any photons) = 0.35 ± 0.11.

25 pp. (1976).

25 pp. (1975).

(1977). doi:10.1016/0370-2693(77)90114-9, The three photon final state produced in e + e − collisions has been measured at the mass of the J ψ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays J ψ → ηγ, η'γ and π o γ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay J ψ → 3γ .

58 pp. (1976).

14 pp. (1977).

(1978). doi:10.1016/0370-2693(78)90742-6, The J/ψ decay modes f 0 (1270)γ and ρπ have been studied in e + e − collision at 3.1 GeV center of mass energy leading to the π + π − γ and π + π − π 0 final states. The f 0 γ decay branching ratio is measured to be (0.20 ± 0.07) × 10 −2 , a value comparable to the J/ψ radiative decay rates into the ηγ and η′γ channels. The J/ψ decay branching ratio into ϱπ is measured to be (1.6 ± 0.4) × 10 −2 .