Measurement of the azimuthal angle distribution of leptons from W boson decays as a function of the W transverse momentum in proton-antiproton collisions at sqrt(s)=1.8 TeV

TL;DR

This paper measures the angular distribution of leptons from W boson decays as a function of W transverse momentum in proton-antiproton collisions, testing QCD effects and Standard Model predictions at Tevatron energies.

Contribution

First measurement of the angular coefficients A_2 and A_3 of W bosons as a function of transverse momentum in proton-antiproton collisions at Tevatron.

Findings

Angular coefficients agree with Standard Model predictions.

QCD effects are observed in W boson production.

Results are consistent with order alpha_s^2 calculations.

Abstract

We present the first measurement of the A_2 and A_3 angular coefficients of the W boson produced in proton-antiproton collisions. We study W-> e+nu and W-> mu+nu candidate events produced in association with at least one jet at CDF, during Run Ia and Run Ib of the Tevatron at sqrt(s)=1.8 TeV. The corresponding integrated luminosity was 110 pb^-1. The jet balances the transverse momentum of the W and introduces QCD effects in W boson production. The extraction of the angular coefficients is achieved through the direct measurement of the azimuthal angle of the charged lepton in the Collins-Soper rest-frame of the W boson. The angular coefficients are measured as a function of the transverse momentum of the W boson. The electron, muon, and combined results are in good agreement with the Standard Model prediction, up to order alpha_s^2 in QCD.