Precise measurement of the [Formula presented] reaction at [Formula presented]

The reaction (Formula presented) has been measured at (Formula presented) based on (Formula presented) 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 (Formula presented) 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 (Formula presented) and (Formula presented) 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.