Measurement of the Lepton Charge Asymmetry inW-Boson Decays Produced inpp¯Collisions

We describe a measurement of the charge asymmetry of leptons from $W$-boson decays in the rapidity range $0<\mathrm{}|y_l|<2.5\mathrm{}$ using $W\to e\nu ,\mu \nu$ events from $110\pm 7{\mathrm{pb}}^{-1\mathrm{}}$ of data collected by the CDF detector during 1992–1995. The asymmetry data constrain the ratio of $d$ and $u$ quark momentum distributions in the proton over the $x$ range of $0.006$ to $0.34$ at $Q^2\approx M_W^2$. The asymmetry predictions that use parton distribution functions obtained from previously published CDF data in the central rapidity region ( $0.0<\mathrm{}|y_l|<1.1\mathrm{}$) do not agree with the new data in the large rapidity region ( $|y_l|>1.1\mathrm{}$).