Abstract
Based on a sample of four million events collected by ALEPH from 1991 to 1995, a measurement of the forward-backward asymmetry in Z -> b-barb decays using inclusive final states is presented. High-performance tagging of b-barb events in a wide angular range is achieved using neural network techniques. An optimal hemisphere charge estimator is built by merging primary and secondary vertex information, leading kaon identification and jet charge in a neural network. The average charge asymmetry, the flavour tagging efficiencies and mean b-hemisphere charges are measured from data and used to extract the pole b asymmetry in the Standard Model A^{0,b}_{FB} = 0.1009 +- 0.0027 (stat) +- 0.0015 (syst), corresponding to a value of the effective weak mixing angle of sin^2(theta_W^{eff}) = 0.23193 +- 0.00056.
Highlights
The measurements of the forward-backward asymmetry of b-quarks from e+e− → Z → bb production offer the most precise determination of the weak mixing angle at LEP
The tracking system consists of two layers of double-sided silicon vertex-detector (VDET), an inner tracking chamber (ITC) and a time projection chamber (TPC)
The data set used for this analysis consists of four million hadronic Z decays recorded by ALEPH during the period 1991 to 1995 in a centre-of-mass energy range of MZ ± 3 GeV
Summary
Dipartimento di Fisica, Universita di Trieste e INFN Sezione di Trieste, I-34127 Trieste, Italy. J. Rothberg Experimental Elementary Particle Physics, University of Washington, Seattle, WA 98195 U.S.A. S.R. Armstrong, K.
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