The lepton charge asymmetry in the decay of W bosons produced in p bar p collisions at √s = 1.8 TeV

The charge asymmetry as a function of rapidity, A(yl), has been measured using the W decays to electrons and muons recorded by CDF during the 1992--93 run of the Tevatron Collider at Fermilab. The luminosity used, approximately 20 pb-1, and detector improvements have lead to a six fold increase in statistics (in the plug region the increase is almost an order of magnitude) making discrimination between sets of parton distributions possible. Our data favors the most recent parton distributions and demonstrates the growing value of collider data in the measurement of the proton's structure