L. Criegee

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 .

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 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

Abstract Photons of 3 GeV and 5 GeV were scattered on 7 different elements, ranging from Be to Au, and detected with a pair spectrometer. The angular distributions show diffractive patterns consistent with known nuclear sizes. Forward cross sections are 20–30% lower than expected from an A 2 dependence. This shadowing effect is qualitatively explained by photon interactions via intermediate hadronic states.

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 We have measured elastic scattering of 5 and 6 GeV photons on hydrogen and deuterium in the angular range 10–50 mrad. On hydrogen we observe a forward diffraction peak with a slope of 8.5 (GeV/c)−2. The extrapolated forward cross sections in units μb/(GeV/c)2 are 0.82 ± 0.04 at 5 GeV and 0.79 ± 0.04 at 6 GeV. They are consistent with the calculated amplitudes obtained from total cross section measurements via the optical theorem and dispersion relations assuming negligible contributions of spin-dependent amplitudes. Deuterium cross sections show a transition from coherent scattering at low |t| to incoherent scattering at higher |t|. They indicate that the isovector exchange amplitude a1 is very small compared to the isoscalar a0. We obtain |a 1 | 2 /|a 0 +a 1 | 2 =0.13±0.09 , Re (a 0 a ∗ 1 )/|a 0 +a 1 | 2 =0.0±0.03, at 5 GeV , |a 1 | 2 /|a 0 +a 1 | 2 =−0.12±0.15 , Re (a 0 a ∗ 1 )/|a 0 +a 1 | 2 =0.10±0.04, at 6 GeV .