L.S. Osborne

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We have measured the cross sections at 90\ifmmode^\circ\else\textdegree\fi{} c.m. for ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\ensuremath{\pi}}^{0}$ photoproduction with polarized photons. The photon energies ranged from 0.8 to 2.2 GeV. We compare the resonant "bumps" in the cross section with theoretical models. The measured asymmetry agrees with a quark-model calculation though the predicted cross sections are low.

We present final measurements of the $Z$ boson-lepton coupling asymmetry parameters ${A}_{e}$, ${A}_{\ensuremath{\mu}}$, and ${A}_{\ensuremath{\tau}}$ with the complete sample of polarized $Z$ bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic $Z$ decays we measure ${A}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.1544\ifmmode\pm\else\textpm\fi{}0.0060$, ${A}_{\ensuremath{\mu}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.142\ifmmode\pm\else\textpm\fi{}0.015$, and ${A}_{\ensuremath{\tau}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.136\ifmmode\pm\else\textpm\fi{}0.015$. Combined with our left-right asymmetry measured from hadronic decays, we find ${A}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.1516\ifmmode\pm\else\textpm\fi{}0.0021$. Assuming lepton universality, we obtain a combined effective weak mixing angle of ${sin}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.23098\ifmmode\pm\else\textpm\fi{}0.00026$.

We have determined the electroweak parameters ${{sin}^{2}\ensuremath{\theta}}_{\mathrm{W}}$ and $\ensuremath{\rho}$ by a measurement of deep-inelastic neutrino-nucleon scattering used a fine-grained neutrino detector exposed to a narrowband neutrino beam at Fermilab. The sampling properties of our detector have permitted neutralcurrent and charged-current events to be well separated over a wide kinematic range, thereby allowing a determination of ${{sin}^{2}\ensuremath{\theta}}_{\mathrm{W}}$ and $\ensuremath{\rho}$ to be made with good statistics and small systematic errors. We have found ${{sin}^{2}\ensuremath{\theta}}_{\mathrm{W}}=0.246\ifmmode\pm\else\textpm\fi{}0.012\ifmmode\pm\else\textpm\fi{}0.013$ in a single-parameter fit.

The cross section for photoproduction of ${\ensuremath{\pi}}^{0}$ mesons was measured at a photon energy of 3 GeV and squared four-momentum transfer ($t$) of -0.1 to -1.2 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ using plane-polarized photons. The asymmetry was found to be consistent with +1.0 for $t$ values above -0.4 and below -1.1. For $\ensuremath{-}0.4<~t<~\ensuremath{-}1.0$ there is a dip in the asymmetry and at $t=\ensuremath{-}0.6$ it drops to 0.55 \ifmmode\pm\else\textpm\fi{} 0.15. This result precludes a simple Regge model with ${\ensuremath{\omega}}^{0}$ and $B$; a theoretical description requires Regge cuts or an ${\ensuremath{\omega}}^{\ensuremath{'}}$ exchange.