Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions

TL;DR

This paper measures the lepton charge asymmetry in W-boson decays from proton-antiproton collisions, providing new constraints on quark distribution functions at high rapidity, revealing discrepancies with previous predictions.

Contribution

It presents the first detailed measurement of lepton charge asymmetry at large rapidity, challenging existing parton distribution models.

Findings

Asymmetry data constrains d/u quark ratio in proton

Discrepancies found between data and existing PDFs at high rapidity

Results improve understanding of proton structure at high x

Abstract

We describe a measurement of the charge asymmetry of leptons from W boson decays in the rapidity range 0<|y_l|<2.5 using W --> enu, munu events from 110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. 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 Q2 \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<|y_l|<1.1) do not agree with the new data in the large rapidity region (|y_l|>1.1).