H. Albrecht

Observation of a Narrow Resonance at 9.46-GeV in electron-Positron Annihilations

Abstract We observe a narrow resonance in the reaction e+e− → hadrons using the DASP detector at the DORIS storage ring. The mass is found to be (9.46 ± 0.01) GeV and the observed width is compatible with the storage ring resolution of ±8 MeV. The energy-integrated cross section results in an electronic width Γee = (1.3 ± 0.4) keV.

Measurement of the decay

Using the ARGUS detector at the e + e − storage ring DORIS II at DESY we have investigated the decays B 0 → D ∗− e + v and B 0 →D ∗− μ + ν. The B 0 mesons were produced in 39600 ϒ(4 S )→ B 0 B 0 decays. Assuming electron-muon universality we obtain a branching ratio BR ( B 0 → D ∗− e + v)= BR ( B 0 → D ∗− γm + ν)=(7.0±1.2±1.9)% .

Evidence for a narrow resonance at 10.01 GeV in electron-positron annihilations

Abstract We observe evidence for a secon narrow resonance in the reation e + e − → hadrons at √s around 10 GeV using the DASP detector at the DORIS storage ring. The mass of the resonance is (10.01 ± 0.02) GeV; its width is in agreement with the storage ring resolution of ≈ 9 MeV. From the integrated cross section, an electronic width of Λ ee = (0.35 ± 0.14) KeV is derived.

Reconstruction of B mesons

Abstract B mesons have been reconstructed in five decay channels of the type B →D ∗ ±nπ(n=1,2,3) using data accumulated by the ARGUS experiment at the e + e − storage ring DORIS II at DESY. In total, we find 40 neutral B mesons above a background of 15±6 events with a mass of (5278.2±1.0±3.0) MeV/ c 2 and 32 charged B mesons above a background of 17±6 events with a mass of (5275.8±1.3±3.0) MeV/ c 2 . The decays B 0 D ∗+ π − π 0 , B 0 D ∗+ π − π − π + , and B − → D ∗+ π − π − π 0 have been observed for the first time. We find substantially smaller branching ratios for the decay modes B 0 → D ∗+ π − and B − → D ∗+ π − π − than previously published by the CLEO collaboration.

Inclusive hadron production in the ϒ-region

Abstract Inclusive production of π ± , K ± and p has been measured in e + e − annihilation for center of mass energies between 9.4 and 10.1 GeV. The hadron yields on the resonances ϒ and ϒ are compared to the off-resonance (continuum) yields with the aim of uncovering differences between three-gluon hadronization and quark-antiquark fragmentation. A noticeable differences is seen in the yield of protons and antiprotons which is (8.1 ± 2.1)% of all charged hadrons for ϒ decay and (18.9 ± 6.9)% of ϒ decay compared to (1.5 ±1.1.)% for non-resonant production.

The hadronic cross section of electron-positron annihilation at 9.5 GeV and the ϒ and ϒ′ resonance parameters

Abstract The reaction e + e − → hadrons has been measured in the ϒ and ϒ′ region using the DASP detector at the DESY storage ring DORIS. The following final results are obtained: R had (9.5 GeV)=3.73±0.16±0.28, Γ ee ( ϒ )=(1.23 ± 0.08 ± 0.12) keV, B μμ ( ϒ )=(3.2±1.3±0.3)%, Γ ee Γ had Γ tot (ϒ′)=(0.55±0.11 ±0.06) keV , and M ( ϒ ′)− M ( ϒ )=(556 ±10) MeV.

Study of the ϒ(9.46) meson in electron-positron annihilations

Abstract New data for the reaction e + e − →ϒ(9.46) have been obtained using the DASP detector at the DORIS storage ring. The electronic width Γ ee is (1.5±0.4) keV. The branching ratio for the decay into muon pairs is (2.5 ± 2.1)%. Energy spectra for inclusive production of hadrons are given.

A determination of the total width of the ϒ(9.46) meson

Abstract Using the DASP detector at the DESY storage ring DORIS we have continued measuring e+e− annihilations near and on the ϒ(9.46) resonance. From the cross sections for e+e− → μ+μ− and e+e− → hadrons we obtain a μ+μ− branching ratio for the ϒ(9.46) of (2.9 ± 1.3 ± 0.5) %, a leptonic width г ee = (1.35 ± 0.11 ± 0.22) keV and a total width of (47−15+37 keV.

Observation of inclusive DS production in B meson decay

Abstract Using the ARGUS detector at the e + e − storage ring DORIS II, we have observed inclusive D S production, using the channel D S − → φπ − , in decays of B mesons produced on the ϒ (4S). The product of branching ratios BR(B→D S X)·BR(D S − → φπ − ) is (4.2±0.9±0.6) × 10 −3 . The D S momentum spectrum suggests a substantial two-body component to the final states of B→D S X decays.