H. Junge

A measurement of the electroweak induced charge asymmetry in e+e−→bb̄☆

Abstract The forward-backward charge asymmetry for the process e + e − → b b → μ ± + hadrons has been measured using the JADE detector at PETRA. An asymmetry of (−22.8 ± 6.0 ± 2.5)% was observed at an average center of mass energy of 34.6 GeV. For comparison, an asymmetry of −25.2% is expected on the basis of the standard Glashow-Salam-Weinberg model.

Measurements of energy correlations ine+e−→hadrons

Energy-energy-correlations (EEC) have been measured with the JADE detector at c.m. energies of 14 GeV, 22 GeV and in the region 29 GeV<Ecm<36 GeV. Corrected results are presented of EEC and their asymmetry, which can be directly compared to theoretical predictions. At 〈Ecm〉=34 GeV a comparison with second order QCD predictions yields good agreement for the string model fragmentation resulting in a value of the strong coupling constant αs=0.165±0.01 (stat.). The independent fragmentation models, which yield values of αs between 0.10 and 0.15 depending on the treatment of energy and momentum conservation and of the gluon splitting, do not provide a satisfactory description of the data over the full angular range.

Comparison of Three Jet Events With {QCD} Shower Models

Distributions of particles in three-jet events from e+e− → hadrons are compared with different fragmentation schemes, i.e. the Lund string model, independent parton fragmentation and QCD shower models. Effects specific to the string scheme, which have been seen in the data, are also reproduced by QCD shower models if soft gluon interference effects are included.

A study of photon production in hadronice+e− annihilation

The production of photons ine+e−→γ+hadrons is investigated at three centre of mass energies around 14, 22 and 34 GeV. On average, photons carry 25% of the total available energy, with a multiplicity similar to the charged multiplicity. The inclusive photon spectra are found to scale with the centre of mass energy as a function of the Feynman variablex. π0 and η mesons are reconstructed from their decay photons. The slopes of the spectra are similar to that for charged pions and approximate scaling is observed for π0 production. The mean π0 and η multiplicities are given. The observed photon yield can be fully accounted for by hadron decays and initial state radiation. However, up to one extra photon per event from other sources cannot be excluded.

SEARCH FOR SUPERSYMMETRIC PARTNERS OF ELECTRONS

Abstract A search for the supersymmetric partners of the electron was made assuming different photino masses. If both types of scalar electrons have an equal mass and the photino is massless, then the lower limit of the scalar electron mass was found to be 25.2 GeV c 2 , whereas, if the scalar electrons have different masses, the lower limit is 21.8 GeV c 2 .

A measurement of the η radiative width Γη→γγ

The radiative width of the η meson has been measured at PETRA in photon-photon collisions. The resulting value is Γη→γγ=0.53±0.04±0.04 keV.

A measurement of the total cross section and a study of inclusive muon production for the process e+e−→ hadrons in the energy range between 39.79 GeV and 46.78 GeV

The total cross section and the inclusive muon cross section for the process e+e−→ hadrons have been measured in the center of mass energy range between 39.79 and 46.78 GeV. The ratio R shows no significant structure. It has an average value of 4.13±0.08±0.14. An upper limit is set on the production of narrow resonances. Limits are obtained for pair-produced heavy quarks. The data are compared with the standard electroweak interaction model including QCD corrections taking into account the five known types of quarks. Upper limits are given for a possible structure of quarks and for effects of color octet leptons.

A search for monojet events produced by virtual Z0 bosons in e+e− annihalation at petra

Abstract A search was performed for the associated production of two different Higgs bosons via a virtual Z 0 in e + e − annihilation (e + e − → h 1 0 h 2 0 ) using the JADE detector at PETRA. This was motivated by the interpretation of the monojet events observed at the CERN p p collider as anomalous Z 0 decays into two neutral Higgs bosons (h 1 0 and h 2 0 ), where h 1 0 is stable and escapes detection while h 2 0 decays into hadrons. Single- or di-jet events with large momentum imbalance are then expected at PETRA energies. No evidence for such events was found in our data; this excludes h 2 0 masses in the range of 1 to 21 GeV with 95% CL, if the branching fraction for Z 0 → h 1 0 h 2 0 is a larger than one half that for Z 0 → v μ v μ . The possibility that the monojets could originate from supersymmetric higgsino production from Z 0 decay is also examined.

A search for massive photinos at petra

Abstract We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e+e− collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c2 at the 95% confidence level, subject to the assumptions d=(100 GeV)2 and m e =40 GeV /c 2 , where d is the supersymmetry breaking scale parameter and m e is the scalar electron mass.

New results one + e −→μ + μ − from the JADE detector at PETRA

AbstractThe production of collinear muon pairs has been studied using the JADE detector at thee+e− storage ring at PETRA. Results for the total cross section and the angular distribution were obtained at centre of mass (cm) energies ranging from 12 to 46 GeV. The data correspond to an integrated luminosity offLdt>90 pb−1, of which 71.2 pb−1 were taken atn