Measurement of the Angular Distribution of Electrons from W to e nu Decays Observed in ppbar Collisions at sqrt(s) = 1.8 TeV

TL;DR

This paper reports the first measurement of the angular distribution parameter alpha2 in W to e nu decays as a function of W transverse momentum, testing next-to-leading order QCD predictions relevant for precise W mass measurements.

Contribution

It provides the first experimental determination of alpha2's dependence on pT(W), offering a crucial test of QCD corrections in W boson decays.

Findings

Measured alpha2 as a function of pT(W)

Confirmed QCD predictions within uncertainties

Improves understanding of W decay angular distributions

Abstract

We present a preliminary measurement of the electron angular distribution parameter alpha2 in W to e nu events using data collected by the D0 detector during the 1994--1995 Tevatron run. We compare our results with next-to-leading order perturbative QCD, which predicts an angular distribution of 1 +/- alpha1 cos theta* +alpha_2 cos^2 theta*, where theta* is the angle between the charged lepton and the antiproton in the Collins-Soper frame. In the presence of QCD corrections, the parameters alpha1 and alpha2 become functions of pT(W), the W boson transverse momentum. We present the first measurement of alpha_2 as a function of pT(W). This measurement is of importance, because it provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W mass measurement.