Model-Independent Measurement of the W-Boson Helicity in Top-Quark Decays at D0

V. M. Abazov et al. (D0 Collaboration)
Phys. Rev. Lett. 100, 062004 – Published 14 February 2008

Abstract

We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1fb1 sample of candidate tt¯ events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron pp¯ Collider. We reconstruct the angle θ* between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting cosθ* distribution finds that the fraction of longitudinal W bosons f0=0.425±0.166(stat)±0.102(syst) and the fraction of right-handed W bosons f+=0.119±0.090(stat)±0.053(syst), which is consistent at the 30% C.L. with the standard model.

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  • Received 31 October 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.062004

©2008 American Physical Society

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Vol. 100, Iss. 6 — 15 February 2008

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