Improved Measurement of the $\bar d / \bar u$ Asymmetry in the Nucleon Sea

FNAL E866/NuSea Collaboration; :; R. S. Towell; P. L. McGaughey

Paper

Improved Measurement of the $\bar d / \bar u$ Asymmetry in the Nucleon Sea

Abstract

Measurements of the ratio of Drell-Yan yields from an 800 \rm{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 anti-down (

) to anti-up (

) quark distributions in the proton sea is determined over a wide range in Bjorken-

. These results confirm previous measurements by E866 and extend them to lower

. From these data,

and

are evaluated for

. These results are compared with parameterizations of various parton distribution functions, models and experimental results from NA51, NMC, and HERMES.