Measurement of sin2 θ lept eff usinge e+e- pairs from γ*/Z bosons produced in pp¯ collisions at a center-of-momentum energy of 1.96 TeV

Abstract

At the Fermilab Tevatron proton-antiproton (pp¯) collider, Drell-Yan lepton pairs are produced in the process pp¯ → e +e − +X through an intermediate γ*/Z boson. The forward-backward asymmetry in the polar-angle distribution of the e − as a function of the e +e −-pair mass is used to obtain sin2 θ lept eff , the effective leptonic determination of the electroweak-mixing parameter sin2 θW . The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.4 fb−1 of integrated luminosity from pp¯ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of sin2 θ lept eff is found to be 0.23248 ± 0.00053. The combination with the previous CDF measurement based on µ +µ− pairs yields sin2 θ lept eff = 0.23221 ± 0.00046. This result, when interpreted within the specified context of the standard model assuming sin2 θW = 1 − M2 W /M2 Z and that the W- and Z-boson masses are on-shell, yields sin2θW = 0.22400 ± 0.00045, or equivalently a W-boson mass of 80.328 ± 0.024 GeV/c2.