Search for Supersymmetry with a dominant R-Parity violating LQD‾LQ\overline{D} Coupling in e+e−e^+ e^- Collisions at centre-of-mass energies of 130 GeV to 172 GeV

A search for pair-production of supersymmetric particles under the assumption that R-parity is violated via a dominant LQDbar coupling has been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The observed candidate events in the data are in agreement with the Standard Model expectation. This result is translated into lower limits on the masses of charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81 GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the 95% confidence level for any generation structure of the LQDbar coupling

A direct measurement of ∣Vcs∣\mid V_{cs} \mid in hadronic W decays using a charm tag

The inclusive charm production rate in W decays is measured from a study of the properties of final state particles. The sample of W pairs is selected from 67.7 pb-1 collected by ALEPH in 1996 and 1997 at centre-of-mass energies near 172 and 183 GeV in the channels W+W- -->4q and W+W- -->lvqq. The branching fraction of hadronic W decays to a final state containing a c quark, R^W_c=Gamma(W-->cX)/Gamma(W-->hadrons), is measured to be 0.51 +- 0.05_stat +- 0.03_syst. This allows a direct determination of the CKM matrix element |V_cs| = 1.00 +- 0.11_stat +- 0.07_syst

Search for R-Parity Violating Decays of Supersymmetric Particles in e+e−e^{+} e^{-} Collisions at Centre-of-Mass Energies near 183 GeV

Searches for pair-production of supersymmetric particles under the assumption that R-parity is violated via a single dominant $LL{\bar E}$, $LQ{\bar D}$ or ${\bar U} {\bar D} {\bar D}$ coupling are performed using the data collected by the \ALEPH\ collaboration at centre-of-mass energies of 181--184~\gev. The observed candidate events in the data are in agreement with the Standard Model expectations. Upper limits on the production cross-sections and lower limits on the masses of charginos, sleptons, squarks and sneutrinos are de rived

Search for R-Parity Violating Decays of Supersymmetric Particles in e+e−e^{+} e^{-} Collisions at Centre-of-Mass Energies near 183 GeV

Searches for pair-production of supersymmetric particles under the assumption that R-parity is violated via a single dominant $LL{\bar E}$, $LQ{\bar D}$ or ${\bar U} {\bar D} {\bar D}$ coupling are performed using the data collected by the \ALEPH\ collaboration at centre-of-mass energies of 181--184~\gev. The observed candidate events in the data are in agreement with the Standard Model expectations. Upper limits on the production cross-sections and lower limits on the masses of charginos, sleptons, squarks and sneutrinos are de rived

Study of fermion pair production in e+ e- collisions at 130-GeV to 183-GeV

The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no significant deviation from the Standard Model predictions. This enable constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale Lambda of eeff contact interactions are typically in the range from 2-10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV for large values of their Yukawa couplings.Comment: 43 pages, 18 figure