Measurement of the angular distribution of electrons fromW→eνdecays observed inpp¯collisions ats=1.8TeV

We present the first measurement of the electron angular distribution parameter α 2 in W→eν events produced in proton-antiproton collisions as a function of the W boson transverse momentum. Our analysis is based on data collected using the DO detector during the 1994–1995 Fermilab Tevatron run. We compare our results with next-to-leading order perturbative QCD, which predicts an angular distribution of (1±α 1 cosθ ∗ +α 2 cos 2 θ ∗ ), where θ ∗ is the polar angle of the electron in the Collins-Soper frame. In the presence of QCD corrections, the parameters α 1 and α 2 become functions of p T W , the W boson transverse momentum. This measurement provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W boson mass measurement.