Limit on the d/u asymmetry of the nucleon sea from Drell-Yan production

We present an analysis of 800-GeV proton-induced Drell-Yan production data from isoscalar targets {sup 2}H and C, and from W, which has a large neutron excess. The ratio of cross sections per nucleon, {ital R}{minus}{sigma}{sub W}/{sigma}{sub IS}, is sensitive to the difference between the {ital {bar d}}({ital x}) and {ital {bar u}}({ital x}) structure functions of the proton. We find that {ital R} is close to unity in the range 0.04{le}{ital x}{le}0.27, allowing upper limits to be set on the {ital {bar d}}-{ital {bar u}} asymmetry. Additionally, the shape of the differential cross section {ital m}{sup 3} {ital d}{sup 2}{sigma}/{ital dx}{sub {ital F}} {ital dm} for {sup 2}H at {ital x}{sub {ital F}}{approx}0 shows no evidence of an asymmetric sea in the proton. We examine the implications of these data for various models of the violation of the Gottfried sum rule in deep-inelastic lepton scattering.