Measuring the u-bar/d-bar asymmetry in the proton sea. Fermilab E866

Experiment E866, conducted at the Fermi National Accelerator Laboratory, is a high statistics experiment to measure u-bar(x)/d-bar(x) in the proton over a wide range of x. A review of the current evidence for u-bar(x) ≠ d-bar(x) in the proton is given and is followed by a short description of the spectrometer and the experimental procedures used in E866. Preliminary results are shown for the ratio of the Drell-Yan cross sections σpd/2σpp. Our preliminary results confirm the conclusions of both the NMC and NA51 collaborations that there is an u-bar(x)/d-bar(x) asymmetry in the proton sea. (author)