R. Schmitz

The total hadronic cross section for e+e− annihilation between 3.1 and 4.8 GeV center of mass energy

Abstract Using the solenoidal magnetic detector PLUTO, we have measured the total cross section for e+e− annihilation into hadrons. Results are presented for center of mass energies between 3.6 and 4.8 GeV, and in the regions of the J ψ (3.1) and ψ(3.7) resonances. We also present results for the 2 prong cross section in the energy range 3.6 to 4.8 GeV.

Evidence for heavy leptons from anomalous μe production in e+e− annihilation

Abstract Events of the type e + e − →μ ± +e ∓ + “nothing” have been observed in the magnetic detector PLUTO at the storage ring DORIS at DESY. The data support the hypothesis of the pair production of heavy leptons, and allow to determine decay parameters. Decay rates into muons and electrons are equal within error, and argue for a new lepton number of the heavy lepton.

Observation of associated Kos-electron production in e+e− annihilation

Abstract We have observed K o s production in e + e − annihilation between 3.6 and 4.4 GeV CMS energy. In the 4.0–4.1 GeV range K o s mesons occur correlated with prompt electrons, indicating the formation and weak decay of charmed particle. Within the sensitivity of the experiment, no K o s -electron correlation is seen at 3.6 and around 4.4 GeV.

Inclusive Ks0-production in e+e− annihilation at energies of 3.6 to 5.0 GeV

Abstract We have measured the production cross section for K s 0 in e + e − annihilation from 3.6 to 5.0 GeV center of mass energy. A substantial increase of the K s 0 yield is observed around 4 GeV in qualitative agreement with the charm hypothesis.

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.

Measurement of the branching ratios for the decays J/ψ(3.1) → fω and J/ψ(3.1) → Bπ

Abstract Decays of the J/ψ (3.1) resonance into final states with four charged and one neutral pion have been investigated. We measured the branching ratios J/ ψ (3.1) → f ω /all = 0.40 ± 0.14)% and J/ ψ (3.1) → (B + π − + B − π + )/all = (0.28 ± 0.07)%.

Inclusive J

We report on inclusive production of Jψ (3.1)-mesons observed in e+e−-annihilation in the energy range s = 4.0–5.0 GeV. After substraction of the radiative tail of the ψ(3.7) direct production of the Jψ (3.1) is found to be in the order of 0.1% of the total hadronic cross section. No enhancements are seen at s = 4.03 GeV and 4.4 GeV. The level is in agreement with expectations from violation of the Zweig-rule.

\psi

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.

production in

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.

e^+ e^-

Abstract The two new, very narrow resonant states discovered at Brookhaven and SLAC were confirmed at the storage ring DORIS of DESY in e + e − -colliding beam experiments.