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.
The e+e- -> ZZ cross section at sqrt(s)=182.7 and 188.6 GeV has been measured using the ALEPH detector. The analysis covers all of the visible ZZ final states and yields cross section measurements of ...sigma_ZZ(182.7 GeV) = 0.11 +- (0.16,0.11) (stat.) +- 0.04 (syst.) pb and sigma_ZZ(188.6 GeV) = 0.67 +- 0.13 (stat.) +- 0.04 (syst.) pb consistent with the Standard Model expectations.
Data collected at centre-of-mass energies of 181-184 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 56.9 pb^-1, are analysed in a search for pair-produced charged Higgs bosons H+-. ...Three analyses are employed to select the tau nu tau nu, tau nu c s and c s c s final states. No evidence for a signal is found. Mass limits are set as a function of the branching fraction B( H+ -> tau+ nu ). Under the assumption that the decay modes considered cover the totality of the possible final states, charged Higgs bosons with masses below 59 GeV/c^2 are excluded at 95% C.L. independently of B( H+ -> tau+ nu ).
Single W production is studied in the data recorded with the ALEPH detector at LEP at centre-of-mass energies between 161 and 183 GeV. The cross section is measured to be sigma_W=0.41+-0.17 (stat) ...+-0.04 (syst) pb at 183 GeV, consistent with the Standard Model expectation. Limits on non-standard WWgamma couplings are deduced as -1.6 < kg < 1.5 (lg=0) and -1.6 < lg < 1.6 (kg=1) at 95% C.L. A search for effectively invisible decays of the W boson in W pair production is performed, leading to an upper limit on the branching ratio of 1.3% (\Gamma_inv= 27 MeV) at 95% C.L.
Inclusive gamma^*gamma interactions to hadronic final states where one scattered electron or positron is detected in the electromagnetic calorimeters have been studied in the LEP 1 data taken by ...ALEPH from 1991 to 1995. The event sample has been used to measure the hadronic structure function of the photon F_2^gamma in three bins with Q^2 of 9.9, 20.7 and 284 GeV^2.
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.
From a study of the kinematic properties of the final state produced in the semileptonic decays b-->X l nu, the inclusive charmless semileptonic branching ratio of b hadrons is measured. With a sam ...ple of 3.6 million hadronic Z decays recorded between 1992 and 1995 with the ALEPH detector at LEP, the value Br(b-->X_u l nu) is determined to be (1.73 +- 0.55_stat +- 0.55_syst)*10^{-3}, where X_u represents any charmless hadronic state and b is a mixture of b hadrons weighted by their production rates. This measurement yields the result |V_ub|^2= (18.68 +- 5.94_stat +- 5.94_syst +- 1 .45_HQE)*10^{-6}, where the last error comes from the conversion of the branching ratio to the CKM matrix element squared.
