Search for narrow resonances in e+e− annihilation at c.m. energies between 29.90 and 31.46 GeV

A search for narrow resonances in e⁺e^? annihilation at c.m. energies between 29.90 and 31.46 GeV provides no evidence for the existence of such states. The 90% confidence upper limit on the integrated resonance cross section is 38 nb MeV, significantly below the value expected for the lowest (t,t?) bound state.     

Search for new flavour production at PETRA

The topological distribution of hadrons from the reaction e⁺e^?→multihadrons has been studied at PETRA energies between $\text{s}\text{=22}\text{and}\text{31.6 GeV}$. No evidence is seen for spherical events which would be expected if massive particles bearing new flavours were produced.     

Total cross section for neutrino charged current interactions at 3 GeV and 9 GeV

Average total cross sections are given for neutrino charged current interactions at neutrino energies of 2.87 GeV and 9.05 GeV. The ratios $\text{〈σ〉}\text{〈E〉}\text{are}\text{0.69 ± 0.05}\text{and}\text{0.61 ± 0.06}$ in units of 10^?38 cm²/GeV nucleon, respectively The errors include both statistical and systematic uncertainties.     

Search for elastic muon-neutrino electron scattering

One possible event of the process ν^?_μ + e^? → v^?_μ + e^? has been observed. The various background processes are discussed and the event interpreted in terms of the Weinberg theory. The 90% confidence limits on the Weinberg parameter are 0.1 < sin²θ_W < 0.6.     

Observation of neutrino-like interactions without muon or electron in the gargamelle neutrino experiment

Events induced by neutral particles and producing hadrons, but no muon or electron, have been observed in the CERN neutrino experiment. These events behave as expected if they arise from neutral current induced processes. The rates relative to the corresponding charged current processes are evaluated.     

A novel approach to confront electroweak data and theory

A novel approach to study electroweak physics at one-loop level in generic SU(2)_L×U(1)_Y theories is introduced. It separates the 1-loop corrections into two pieces: process specific ones from vertex and box contributions, and universal ones from contributions to the gauge boson propagators. The latter are parametrized in terms of four effective form factors $\bar e^2 (q^2 ), \bar s^2 (q^2 ), \bar g_Z^2 (q^2 )$ and $\bar g_W^2 (q^2 )$ corresponding to the γγ, γZ,ZZ andWW propagators. Under the assumption that only the Standard Model contributes to the process specific corrections, the magnitudes of the four form factors are determined atq ²=0 and atq ²=m _Z ² by fitting to all available precision experiments. These values are then compared systematically with predictions of SU(2)_L×U(1)_Y theories. In all fits α _s (m _Z ) and $\bar \alpha (m_Z^2 )$ are treated as external parameters in order to keep the interpretation as flexible as possible. The treatment of the electroweak data is presented in detail together with the relevant theoretical formulae used to interpret the data. No deviation from the Standard Model has been identified. Ranges of the top quark and Higgs boson masses are derived as functions of α _s (m _Z ) and $\bar \alpha (m_Z^2 )$ . Also discussed are consequences of the recent precision measurement of the left-right asymmetry at SLC as well as the impact of a top quark mass and an improvedW mass measurement.     

The running of the electromagnetic coupling $\alpha$ in small angle Bhabha scattering

A method to determine the running of from a measurement of small angle Bhabha scattering is proposed and worked out. The method is suited to high statistics experiments at e ⁺ e^--colliders which are equipped with luminometers in the appropriate angular region. A new simulation code predicting small angle Bhabha scattering is also presented.Received: 22 January 2004, Published online: 16 March 2004L. Trentadue: Permanent address: Dipartimento di Fisica, Universitá di Parma and INFN, Gruppo Collegato di Parma, 43100 Parma, Italy     

Elektronenstoßanregung und Polarisation der He II-Fowler-α-Linie

The hydrogen-like He II-Fowler-α-(λ=4686 Å)-line has been excited by single electron impact collisions with ground-state helium atoms. The excitation-ionization function was measured from the threshold (76 eV) to 300 eV in a pressure-independent range. A broad maximum of the excitation-ionization function was observed at 200 eV. The line excited by a parallel electron beam has been proved polarized in the energy range quoted above. The degree of polarization increased monotonously from 6% at 300 eV to 13% near the excitation threshold. Comparison was made with previous experimental work. No polarization of the Fowler-α-Line was reported in other investigations. The shape of the excitation-ionization function agrees with that ofJohn andLin. Comparison with theoretical calculations is not as yet possible because only results of Born approximations are available.