Improved measurement of the d¯/ū asymmetry in the nucleon sea

Measurements of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on liquid hydrogen and deuterium targets are reported. Approximately 360 000 Drell-Yan muon pairs remained after all cuts on the data. From these data, the ratio of down antiquark ((d) over bar) to up ((u) over bar) antiquark distributions in the proton sea is determined over a wide range in Bjorken-x. These results confirm previous measurements by E866 and extend them to lower x. From these data, ((d) over bar-(u) over bar) and integral((d) over bar-(u) over bar )dx are evaluated for 0.015更多