Improved Direct Measurement of the Parity-Violation Parameter Ab Using a Mass Tag and Momentum-Weighted Track Charge

Le résumé fourni par la source

We present an improved direct measurement of the parity-violation parameter ${A}_{b}$ in the $Z$ boson--$b$-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in $Z\ensuremath{\rightarrow}b\overline{b}$ events via the topological reconstruction of the $B$ hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of ${A}_{b}$ to be made independently of other $Z$-pole coupling parameters. From the 1996--1998 sample of 400 000 hadronic $Z$ decays, produced with an average beam polarization of 73.4%, we find ${A}_{b}=0.906\ifmmode\pm\else\textpm\fi{}0.022(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.023(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$.

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