0000000000162440
AUTHOR
Grauges E
Study of the fragmentation of b quarks into B mesons at the Z peak
The fragmentation of b quarks into B mesons is studied with four million hadronic Z decays collected by the ALEPH experiment during the years 1991-1995. A semi-exclusive reconstruction of B->l nu D(*) decays is performed, by combining lepton candidates with fully reconstructed D(*) mesons while the neutrino energy is estimated from the missing energy of the event. The mean value of xewd, the energy of the weakly-decaying B meson normalised to the beam energy, is found to be mxewd = 0.716 +- 0.006 (stat) +- 0.006 (syst) using a model-independent method; the corresponding value for the energy of the leading B meson is mxel = 0.736 +- 0.006 (stat) +- 0.006 (syst). The reconstructed spectra …
Measurement of triple gauge WWγ couplings at LEP2 using photonic events
A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV,corresponding to a total integrated luminosity of about 80 pb**-1.The measured distributions are in agreement with Standard Model predictions, leading to constraints on W W gamma gauge coupling parameters Delta(kappa_gamma) and lambda_gamma. The results from the fit to the cross sectionsand to the energy and angular distributions of the photons are: Delta(kappa_gamma) = 0.05 +1.15/-1.10 (stat) +/- 0.25 (syst) lambda_gamma = 0.05 +1.55/-1.45 (stat) +/- 0.30 (syst) A study of events with photons and missing energy has been pe…
Search for Single Top Production in $e^{+} e^{-}$ Collisions at $\sqrt{s}$ up to 209 GeV
Single top production via the flavour changing neutral current reactions e+e- -> \bar{t}c, \bar{t}u is searched for within the 214 pb-1 of data collected by ALEPH at centre-of-mass energies between 204 and 209 GeV. No deviation from the Standard Model expectation is observed and upper limits on the single top production cross sections are derived. The combination with data collected at lower centre-of-mass energies yields an upper limit on the branching ratio BR(t -> Zc)+BR(t -> Zu) 14%, for BR(t -> ��c)+BR(t -> ��u)= 0 and mt=174 GeV/c2.