A. F. Garfinkel

Observation of a Narrow Resonance Formed in e+ e- Annihilation at 9.46-GeV

Abstract An experiment using the PLUTO detector has observed the formation of a narrow, high mass, resonance in e+e− annihilations at the DORIS storage ring. The mass is determined to be 9.46±0.01 GeV which is consistent with that of the Upsilon. The gaussian width σ is observed as 8±1 MeV and is equal to the DORIS energy resolution. This suggests that the resonance is a bound state of a new heavy quark-antiquark pair. An electronic width Γee=1.3±0.4 keV was obtained. In standard theoretical models, this favors a quark charge assignment of 1 3 .

A study of jets in electron positron annihilation into hadrons in the energy range 3.1 to 9.5 GeV

Abstract From an analysis of data taken with the detector PLUTO and the DORIS storage rings we have obtained evidence for jet structure in e + e − annihilation with hadrons. Results for mean sphericity, mean thrust, the angular dependence of the jet axis and for 〈 p t 〉 and 〈 p ∥ 〉 with respect to the jet axis are presented. At 9.4 GeV we also discuss the angular dependence of the charged and neutral deposited energy with respect to the jet axis.

Jet analysis of the ϒ(9.46) decay into charged hadrons

Abstract The direct decay into four and more charged particles of the ϒ(9.46) formed in e+e− collisions is analysed for hadron-jet configurations. The results are compared with the expectations of phase space, a q q two-jet model and a QCD three-gluon decay mechanism. Out of these three models, the three-gluon decay describes best the data.

Evidence for the τ → νϱπ decay mode

Abstract Annihilation of e+e− into final states with a single electron has been studied with the PLUTO detector at the DORIS storage ring at CMS energies from 3.6 to 5 GeV. In the sample of 4-prong events without any detected photon we observe 21 events which we assign to the reaction e+e− → τ+τ− → ννe + νϱ0π. We obtain a branching ratio for τ+ → νϱ0π+ of 0.050 ± 0.015 with an overall systematic uncertainty of 30%. The data are consistent with the ϱπ coming from an A1 meson.

Determination of the electronic branching ratio of the ϒ(9.46) and an upper limit for its total width

Abstract We have measured the reaction e + e − → e + e − at the ϒ Using athe excess of electron pairs over the QED expectation we obtain an electronic branching ratio of B ee = (5.1 ± 3.0) %. Combining this with publishe values of the muonic branching ratio B μμ we conclude that the ϒ is a narrow state with a total width

Measurement of leptonic branching ratios of the Γ(9.46)

The electronic width Γee and the muonic branching ratioBμμ=Γμμ/Γtot of the Γ(9.46) have been measured as Γee=(1.33±0.14) andBμμ=(2.2±2.0)%. From these values a lower limit of Γtot<23keV for the total width of the Γ(9.46) is obtained.

Measurement of the f0(1270) polarization in the J/ψ → f0 γ decay☆

Abstract The polarization of the f 0 (1270) and ϱ 0 (770) produced in the J/ ψ decays into f 0 γ and ϱ 0 π 0 are measured in e + e − collisions at 3.1 GeV. A fit to the f 0 production and decay angular distributions yields the values A 1 / A 0 = 0.6 ± 0.3 and A 2 / A 0 = 0.3 −1.6 +0.6 , where A λ are the f 0 helicity amplitudes. These results are in good agreement with the values predicted from a QCD two-gluon-exchange model. In addition an upper limit of 2.3 × 10 −4 is obtained for the J/ ψ → f ′ 0 (1514) γ decay branching ratio which implies Γ (J/ ψ → f ′ γ )/ Γ (J/ ψ → f 0 γ ) ⩽ 0.12 ± 0.05.

Spin parity analysis of the decay τ→νρπ

We have studied the τ→νρ0π decay in data taken with the PLUTO detector at the DORISe+e− storage ring, at CM energies from 4 to 5 GeV. We have found 27 events with the τ→νρ0π decay mode corresponding to a branching ratio ofB=(5.4±1.7)%. The Dalitz plot and theρ0π mass spectrum are analysed for the ρπ partial wave and spin state. Only theρ0πs-wave as produced by the axial vector current gives a good description. Theρ0π mass spectrum is suggestive of anA1 resonance. An upper limit on τ±→vπ±π+π− withoutρ0 formation is given.

Observation of the decay τ → πv

Abstract The decay of the heavy lepton τ into πv has been established using the magnetic detector PLUTO. The branching ratio is determined to be BR( τ → πv )=(9.0 ± 2.9)% with an additional systematic uncertainty of 2.5%. This value is in good agreement with the theoretical prediction.

An experimental upper limit for the τ lifetime

Abstract Two methods for setting an upper limit on the τ lifetime using events assigned to τ + τ - production in e + e - annihilation in the centre of mass energy range 3.9 to 5 GeV are discussed. The combined result is a 95% CL upper limit for the τ lifetime of 9.0 × 10 −12 .