0000000000517264
AUTHOR
J M. Pascolo
Measurement of W-pair production in $e^{+}e^{-}$ collisions at centre-of-mass energies from 183 to 209 GeV
The W + W- production cross section is measured from a data sample corresponding to a total integrated luminosity of 683 pb-1, collected by the ALEPH experiment at LEP at centre-of-mass energies from 183 to 209 GeV. Individual cross sections for the different topologies arising from W decays into leptons or hadrons, as well as the total W-pair cross section are given at eight centre-of-mass energies. The results are found to be in agreement with recently developed Standard Model calculations at the one percent level. The hadronic branching fraction of the W boson is measured to be B(W→qq¯) = 67.13 ± 0.37(stat.) ± 0.15(syst.)%, from which the CKM matrix element |\ensuremathVcs| is determined…
Search for neutral Higgs bosons decaying into four taus at LEP2
A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb-1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, β2 = σ(e+e -→Zh)/σSM(e+e-→Zh) ×B(h→aa)×B(a→τ+τ-) 2. For mh 1 is excluded at the 95% confidence level.
Constraints on anomalous QGC's in $e^{+}e^{-}$ interactions from 183 to 209 GeV
The acoplanar photon pairs produced in the reaction e+ e- --> nu nubar gamma gamma are analysed in the 700 inverse nanobarns of data collected by the ALEPH detector at centre-of-mass energies between 183 and 209 GeV. No deviation from the Standard Model predictions is seen in any of the distributions examined. The resulting 95% C.L. limits set on the anomalous QGC's, az_0, az_c, aw_0 and aw_c, are -0.012 GeV**-2 < az_0/Lambda**2 < +0.019 GeV**-2, -0.041 GeV**-2 < az_c/Lambda**2 < +0.044 GeV**-2, -0.060 GeV**-2 < aw_0/Lambda**2 < +0.055 GeV**-2, -0.099 GeV**-2 < aw_c/Lambda**2 < +0.093 GeV**-2, where Lambda is the energy scale of the new Physics responsible for the anomalous couplings.
Studies of QCD at $e^{+}e^{-}$ centre-of-mass energies between 91 and 209 GeV
The hadronic final states observed with the ALEPH detector at LEP in e(+)e(-) annihilation are analysed using 730 pb(-1) of data collected between 91 and 209 GeV in the framework of QCD. In particular event-shape variables and inclusive charged particle spectra are measured. The energy evolution of quantities derived from these measurements is compared to analytic QCD predictions. The mean charged particle multiplicity, the charged particle momentum spectrum and its peak position are compared to predictions of the modified-leading-logarithmic approximation. The strong coupling constant alpha(s) is determined from a fit of the QCD prediction to distributions of six event-shape variables at e…