Precise measurement of the $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ reaction at $\sqrt{s}=57.77\hspace{1em}\mathrm{GeV}$

The reaction $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ has been measured at $\sqrt{s}=57.77\mathrm{GeV},$ based on $289.6\pm 2.6\hspace{0.5em}{\mathrm{pb}}^{-1}$ data collected with the VENUS detector at TRISTAN. The production cross section is measured in bins of the production angle within an angular acceptance of $|\cos \theta |<~0.75,$ according to a model-independent definition. The result is consistent with the prediction of the standard electroweak theory. Although a trend in measurements at lower energies that the total cross section tends to be smaller than the prediction remains, the discrepancy is not significant. The model-independent result is converted to the differential cross section in the effective-Born scheme by unfolding photon-radiation effects. This result can be extrapolated to quantities for the full solid angle as ${\sigma }_{\mathrm{tot}}^{\mathrm{EB}}=30.05\mathrm{}\pm 0.59\hspace{0.5em}\mathrm{pb}$ and $A_{\mathrm{FB}}^{\mathrm{EB}}=-0.350\pm 0.017,$ by imposing an ordinary assumption on the production-angle dependence. The converted results are used to set constraints on extensions of the standard theory. S-matrix parametrization, and possible contributions from contact interactions and heavy neutral-scalar exchanges are examined.