Precise determination of

Measurements of the semileptonic weak neutral-current reactions ..nu../sub ..mu../p..--> nu../sub ..mu../p and nu-bar/sub ..mu../p..-->..nu-bar/sub ..mu../p which yield the absolute differential cross sections dsigma(..nu../sub ..mu../p)/dQ/sup 2/ and dsigma(nu-bar/sub ..mu../p)/dQ/sup 2/ described. The weak-neutral-current parameter, sin/sup 2/theta/sub W/, is determined to be sin/sup 2/theta/sub W/ = 0.220 +- 0.016 (stat)/sub -0.031//sup +0.023/(syst).