First Measurement of the Left-Right Charge Asymmetry in HadronicZBoson Decays and a New Determination ofsin2θWeff

Abstract

We present the first measurement of the left-right charge asymmetry ${A}_{Q}^{\mathrm{obs}}$ in hadronic $Z$ boson decays. This was performed at ${E}_{\mathrm{c}.\mathrm{m}.}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}91.27\mathrm{GeV}$ with the SLD at the SLAC Linear Collider with a polarized electron beam. Using 89 838 events we obtain ${A}_{Q}^{\mathrm{obs}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.225\ifmmode\pm\else\textpm\fi{}0.056\ifmmode\pm\else\textpm\fi{}0.019$, which leads to a measurement of the electron left-right asymmetry parameter, ${A}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.162\ifmmode\pm\else\textpm\fi{}0.041\ifmmode\pm\else\textpm\fi{}0.014$, and ${sin}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2297\ifmmode\pm\else\textpm\fi{}0.0052\ifmmode\pm\else\textpm\fi{}0.0018$. Also, the ${A}_{Q}^{\mathrm{obs}}$ measurement combined with the left-right cross section asymmetry determines ${A}_{e}$ independent of the value of the electron-beam polarization.