Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its avour independence, tests of the SU(3) gauge structure of QCD, study of coherence eects, and measurements of single-particle inclusive distributions and two-particle correlations for many identied baryons and mesons.
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 --> lvD((*)) 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 x(B)(wd), the energy of the weakly-decaying B meson normalised to the beam energy, is found to be (x(B)(wd)) = 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 (x(B)(L)) = 0.736 +/- 0.006 (stat) +/- 0.006 (syst). The reconstructed spectra are compared with different fragmentation models. (C) 2001 Published by Elsevier Science B.V
A search has been performed for the Standard Model Higgs boson in the data sample collected with the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV. An excess of 3 sigma beyond the background expectation is found, consistent with the production of the Higgs boson with a mass near 114 GeV/c(2). Much of this excess is seen in the four-jet analyses, where three high purity events are selected. (C) 2000 Elsevier Science B.V. All rights reserved
The flavour changing neutral current decay b-->sγ has been detected in hadronic Z decays collected by ALEPH at LEP. The signal is isolated in lifetime-tagged bb¯ events by the presence of a hard photon associated with a system of high momentum and high rapidity hadrons. The background processes are normalised from the data themselves. The inclusive branching ratio is measured to beconsistent with the Standard Model expectation via penguin processes
(To be submitted to Nucl. Instr. Meth. A) described. electrons, muons, neutrinos (from missing energy), charged hadrons, ·rr°'s and V°'s is of the detector is its ability to identify particles; the performance in identification of hadrons, and the accuracy obtained in energy and angle is given. An essential property of charged tracks is specified. Calorimeters are used to measure photons and neutral accuracy of the tracking detectors to measure the impact parameter and momentumThe performance of the ALEPH detector at the LEP e+e' collider is reviewed. The Abstract The ALEPH Collaboration" Performance of the ALEPH detector at LEP
This article represents the recommendations for the management of spontaneous intracerebral haemorrhage of the European Stroke Initiative (EUSI). These recommendations are endorsed by the 3 European societies which are represented in the EUSI: the European Stroke Council, the European Neurological Society and the European Federation of Neurological Societies.
The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization isPΛL = -0.32 +/- 0.07 for z = p/pbeam > 0.3. This agrees with the prediction of -0.39 +/- 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛΛ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction
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