Heavy flavour production in Z decays

From an analysis of inclusive leptons in data collected by the ALEPH detector at LEP, we measure the fractions of b and c events in hadronic Z decays. The b fraction times semileptonic branching ratio is measured to be . Assuming a b semileptonic branching ratio of 0.102 ± 0.010 gives , in good agreement with the standard model prediction of 0.217. The c fraction times semileptonic branching ratio is measured to be . Assuming a c semileptonic branching ratio of 0.090 ± 0.013 gives , in agreement with the standard model prediction of 0.171

Search for the neutral Higgs bosons of the MSSM and other two doublet models

Large radiative corrections modify the predictions of the minimal supersymmetric extension of the standard model (MSSM) sufficiently for the constraints on this model, formerly derived from the searches for the CP-even h and for the CP-odd A neutral Higgs bosons, to be invalidated. In particular, the new h → AA decay mode has to be considered. The results presented here have been obtained from a data sample corresponding to about 185000 hadronic Z decays collected by the ALEPH experiment at LEP. No indication for any signal of the reactions or e+e− → hA was found. A domain in the (mh,mA) plane is thus excluded at 95% CL in a large class of two-Higgs-doublet models. More restrictive results are derived in the MSSM, with one loop radiative corrections to the Higgs potential taken into account. It is found that mh > 41 GeV/c2 and mA > 20 GeV/c2 at 95% CL when the other parameters of the model are varied in their allowed ranges

A search for pair-produced charged Higgs bosons in Z0 decays

A search for pair-produced charged Higgs bosons in decays of the Z0 has been performed using the ALEPH detector at LEP for the decay channels . Searches for two additional decay channels in which cs is replaced by cb were also performed. With 1.17 pb−1 of integrated luminosity, corresponding to about 25 000 hadronic decays of the Z0, the charged Higgs has been excluded at 95% CL in the mass range 7.6 to 43.0 GeV for BR[H± → ντ] = 100%, 8.3 to 40.6 GeV for BR[H±→ντ] = BR[H±→cs] = 50%, and 14.4 to 35.4 GeV for BR[H±→cs] = 100% . With cs replaced by cb, the charged Higgs has been excluded at 95% CL in the mass range 12.0 to 40.7 GeV for BR[H±→ντ] = BR[H±→cb] = 50%, and 16.2 to 35.7 GeV for BR[H±→cb] = 100%

Measurement of alpha-s from the structure of particle clusters produced in hadronic Z decays

Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant αs is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, Ycut, before these variables are computed. The combined result from all shape variables of pre-clustered events is αs(MZ2 = 0.117±0.005 for a renormalization scale . For μ values between MZ and the b-quark mass, the result changes by −0.009+0.006

Electroweak parameters of the Z0^0 resonance and the standard model

Media temporalities of the elderly : evolutions in stability This article shows the context of analysis and the first results of a research on media temporalities of the elderly. Several works have finely analysed the diversity of the media practices and studied meanings of media uses. I wish to continue these analyses by insisting on the evolutionary and dynamic aspect of the practices and temporalities of users having expanded, enhanced, so called "interactive" radio and especially television programming. A priori, the elderly, upon retirement, have a "full-time free time". Their media practices seem strongly influenced by their first experiments ; the appropriation of the various peripheral accessories which gradually came with the media, to the latest digital ones, seems to reinforce their habits of watching television. Their representations and relations with times and media are very far away from the image of television like omnipresent media or "devourer of time". Rather, their media practices are to be understood like a temporality of the occupation, according to the expression of Gerard Derèze, characterized by interest and utility. A particular glance at the users who do not carry out a systematic selection of the programs, accepting the unforeseen, highlights an approach of media and time that allow "useful encounter" which I would qualify in a first stage by : "chance and encounter" and "random and the following". The few points presented here make me assume that the global relation of the autonomous elderly persons to the media can evolve when confronted to their new temporal framework and the new program offer, whereas their representations and use of the media remain quite stable

Electroweak parameters of the Z0^0 resonance and the standard model

Media temporalities of the elderly : evolutions in stability This article shows the context of analysis and the first results of a research on media temporalities of the elderly. Several works have finely analysed the diversity of the media practices and studied meanings of media uses. I wish to continue these analyses by insisting on the evolutionary and dynamic aspect of the practices and temporalities of users having expanded, enhanced, so called "interactive" radio and especially television programming. A priori, the elderly, upon retirement, have a "full-time free time". Their media practices seem strongly influenced by their first experiments ; the appropriation of the various peripheral accessories which gradually came with the media, to the latest digital ones, seems to reinforce their habits of watching television. Their representations and relations with times and media are very far away from the image of television like omnipresent media or "devourer of time". Rather, their media practices are to be understood like a temporality of the occupation, according to the expression of Gerard Derèze, characterized by interest and utility. A particular glance at the users who do not carry out a systematic selection of the programs, accepting the unforeseen, highlights an approach of media and time that allow "useful encounter" which I would qualify in a first stage by : "chance and encounter" and "random and the following". The few points presented here make me assume that the global relation of the autonomous elderly persons to the media can evolve when confronted to their new temporal framework and the new program offer, whereas their representations and use of the media remain quite stable