Measurement of the b ---> tau- anti-tau-neutrino X branching ratio

Using a missing energy tag, evidence is presented for the decay b ---> tau- anti-tau-neutrino X, and its branching ratio is measured to be (4.08 ± 0.76 ± 0.62)%

Measurement of prompt photon production in hadronic Z decays

The production of isolated photons in hadronicZ decays is measured with the ALEPH detector at LEP using a sample of 450 000 hadronic events. The corrected rate is given for several values of the minimum invariant mass squared cut between the photon and the jets. This measurement of final state radiation from the quarks is compared with the predictions of parton shower models JETSET, ARIADNE and HERWIG as well as with the predictions of QCD matrix element calculations

Search for a nonminimal Higgs boson produced in the reaction e+ e- ---> h Z*

A data sample corresponding to 1.23 million hadronic Z decays collected by the ALEPH detector at LEP has been searched for signals of the production of a non-minimal CP-even Higgs boson h in the reaction e+e- --> hZ*. The h decay modes considered were: those of the minimal standard model Higgs boson, with modified branching ratios; decays into a pair of CP-odd Higgs bosons A; and decays into invisible final states. Only one event was found, a very acoplanar e+e- pair which could originate from the standard model background process e+e- --> e+e- nu (nu) over bar. Upper limits for the cross-section of the reaction e+e- --> hZ* have been derived as a function of m(h), the mass of the Higgs boson h. In the case of invisible decays, the 95% CL lower limit on m(h) is 65 GeV/c(2) for a production cross-section equal to that of a minimal standard model Higgs boson. When combined with previous ALEPH results on the reaction e+e- --> hA, these cross-section upper limits exclude a domain in the (m(h), M(A)) plane of the MSSM such that, if invisible h and A decays can be neglected, 95% CL lower limits of 44 and 21 GeV/c(2) result for m(h) and m(A), respectively, independent of the other parameters of the model

Properties of hadronic events in e+e− annihilation at S(1/2)S^(1/2) = 91-GeV

We report on properties of hadronic events from e+e− annihilation observed by the ALEPH detector at the large Electron Positron Collider at CERN. The center-of-mass energy was . Measured distributions of the global event-shape variables sphericity, aplanarity, thrust and minor value, and of the inclusive variables xp, p⊥in, p⊥out and y are presented. We measure a mean charged multiplicity in hadronic events of 〈Nch〉=21.3±0.1 (statistical)±0.6 (systematic). The data are in good agreement with QCD-based models which use the leading-logarithm approximation, and are less well described by a model using O(αs2) QCD

Search for neutral Higgs bosons from supersymmetry in Z decays

The light scalar Higgs boson h and the pseudoscalar Higgs boson A of the minimal supersymmetric standard model have been searched for in the processes e+ e- -> h f fbar and e+e−->hA using data collected by ALEPH at the LEP e+e− collider, with center of mass energies at and near the Z peak. Using a variety of signatures adapted to various mass ranges for h and A, we have excluded a large domain in the parameter space. For large values of nu_2/nu_1, the ratio of the vacuum expectation values of the two Higgs fields, the whole range from 0 to 38.8 GeV is excluded for Mh and MA at 95% CL