P. Schmüser

Radiative decays of the Jψ and evidence for a new heavy resonance

Abstract 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, ηγ and πoγ 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 .

Charged pion, kaon, proton and antiproton production in high energy e+e− annihilations

Abstract Production of pions, kaons, protons and antiprotons has been studied in e + e − annihilations at 12 and 30 GeV centre of mass energy using time of flight techniques. The fractional yield of charged kaons and baryons appears to rise with outgoing particle momentum. At our highest energy at least 40% of e + e − annihilations into hadrons are estimated to contain baryons.

PION PRODUCTION WITH POLARIZED PHOTONS AND TEST OF VECTOR DOMINANCE MODEL.

Abstract Cross section asymmetries for the sum of single π+ and π- production with polarized photons of 3.4 GeV have been measured. The results disagree with calculations based on the vector dominance model using experimental data of vector meson production in π beams.

Evidence for Weakly Decaying New Hadrons in e+ e- Collisions Above 4-GeV CMS

Abstract Single electrons produced with hadrons in e + e − collisions at cms energies of 4.0 to 4.2 GeV have been observed at DORIS using the double arm spectrometer DASP. The measured electron spectrum peaks at low momentum and the associated hadron multiplicity is high. These experimental results are consistent with the electromagnetic production and weak decay of a hadron with a new quantum number that is conserved by the strong and electromagnetic interaction. The electron yield at 3.7 GeV (the ψ′ resonance) and at lower energies was found to be consistent with the estimated background, indicating that the production threshold lies between 3.7 and 4.0 GeV.

Inclusive hadron production by e+e− annihilation for s between 13 and 25 GeV2

Abstract Charged hadron production via e + e − → h ± X where h ± = π ± , K ± , p has been measured for s values between 13 and 25 GeV2. Inclusive cross sections and the evidence for scaling are presented.

Evidence for the F meson

Abstract Inclusive η production by e + e − annihilation for cm energies between 4 and 5.2 GeV was studied. A strong η signal was observed at 4.4 GeV, produced predominantly in conjunction with a low energy photon suggestive of F F ∗ or F ∗ F ∗ production. From events containing a π ± , and η, and a low energy photon the F and F ∗ masses were found to be 2.03 ± 0.06 and 2.14 ± 0.06 GeV, respectively.

π+ production with linearly polarized photons

Abstract Single π+ production on protons by linearly polarized photons of 2.5 to 5 GeV was measured at squared four momentum transfers t between −0.01 and −0.6 (GeV/c)2. The results show that the differential cross section d σ ⊥ d t with the electric vector of the photon perpendicular to the reaction plane is much larger than d σ ‖ d t with the electric vector parallel to the reaction plane. The predictions of Regge models and of the vector meson dominance model are briefly discussed.

Inclusive ϱ0 production in e+e− annihilation at high energy

We have observed ϱ0 production in e+e− annihilation to hadrons at high energies. The differential cross section at a centre of mass energy W, of 34 GeV, is presented. In the range 0.2< x < 0.7, we measure 0.33 ± 0.06 (stat.) ± 0.07 (syst.), 0.22 ± 0.06 ± 0.05 and 0.22 ± 0.02 ± 0.05 ϱ0/event at W = 14, 22 and 34 GeV respectively.

Test of QED in e+e− annihilation at energies between 12 and 31.6 GeV

We have measured the reactions e+e− → e+e− → μ+μ− and e+e− → γγ at c.m. energies between 12 and 31.6 GeV. Excellent agreement with the predictions of QED has been found, resulting in cut off parameters Λ+ > 112 GeV and Λ− > 139 GeV for the first process and Λ+ > 34 GeV and Λ− > 42 GeV (95% c.1.) for the last one. A limit on the Weinberg angle of sin2θW < 0.55 (95% c.1.) has been obtained.

Production characteristics of the F meson

Inclusive cross sections of η production by e+e- annihilation for c.m. energies between 4.0 and 5.0 GeV are presented. The η production is shown to be correlated with the production of a weakly decaying particle, indicating that its main source is F production. At the 4.42 GeV resonance it is correlated with a low energy photon, suggesting FF∗ or F∗F∗ production. A mass determination of the F is made at 4.42 GeV using the F → ηπ decay channel.