Measurement of W-pair production in e+e−e^+ e^- collisions at 189 GeV

The production of W-pairs is analysed in a data samplecollected by ALEPH at a mean centre-of-mass energy of 188.6 GeV,corresponding to an integrated luminosity of 174.2 pb^-1. Crosssections are given for different topologies of W decays intoleptons or hadrons. Combining all final states and assumingStandard Model branching fractions, the total W-pair cross sectionis measured to be 15.71 +- 0.34 (stat) +- 0.18 (syst) pb.Using also the W-pair data samples collected by ALEPH at lowercentre-of-mass energies, the decay branching fraction of the W bosoninto hadrons is measured to be BR (W hadrons) = 66.97+- 0.65 (stat) +- 0.32 (syst) %, allowing a determination of theCKM matrix element |V(cs)|= 0.951 +- 0.030 (stat) +- 0.015 (syst)

Searches for neutral Higgs bosons in e+e−e^{+}e^{-} collisions at centre-of-mass energies from 192 to 202 GeV

Searches for neutral Higgs bosons are performed with the 237 pb^-1 of data collected in 1999 by the ALEPH detector at LEP, for centre-of-mass energies between 191.6 and 201.6 GeV. These searches apply to Higgs bosons within the context of the Standard Model and its minimal supersymmetric extension (MSSM) as well as to invisibly decaying Higgs bosons. No evidence of a signal is seen. A lower limit on the mass of the Standard Model Higgs boson of 107.7 GeV/c^2 at 95% confidence level is set. In the MSSM, lower limits of 91.2 and 91.6 GeV/c^2 are derived for the masses of the neutral Higgs bosons h and A, respectively. For a Higgs boson decaying invisibly and produced with the Standard Model cross section, masses below 106.4 GeV/c^2 are excluded

Single vector boson production in e+e− collisions at centre-of-mass energies from 183 to 209 GeV

The cross sections for single vector boson production in the Weν and Zee channels are measured from the data collected by the ALEPH detector at LEP for centre-of-mass energies between 183 and 209 GeV. These data correspond to a total integratedluminosity of 683 pb−1. Single-W production is studied in both hadronic and leptonic decay channels. Hadronic and dimuon decays are used for single-Z production. The measured cross sections agree with the Standard Model predictions

Measurement of the hadronic photon structure function F2(gamma)(x, Q**2) in two-photon collisions at LEP

The hadronic photon structure function Fγ2(x,Q2) is measured from data taken with the ALEPH detector at LEP. At centre-of-mass energies between s√=189GeV and 207GeV an integrated luminosity of 548.4pb−1 is analyzed in two ranges of Q 2 with ⟨Q2⟩=17.3 GeV2 and 67.2 GeV2. Detector effects and acceptance are corrected for with a Tikhonov unfolding procedure. The results are compared to theoretical predictions and measurements from other experiments