# Model-independent measurement of the W boson helicity in top quark decays

Abstract : We present the first model-independent measurement of the helicity of $W$ bosons produced in top quark decays, based on a 1 fb$^{-1}$ sample of candidate $t\bar{t}$ events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider. We reconstruct the angle $\theta^*$ 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 \costheta distribution finds that the fraction of longitudinal $W$ bosons $f_0 = 0.425 \pm 0.166 \hbox{(stat.)} \pm 0.102 \hbox{(syst.)}$ and the fraction of right-handed $W$ bosons $f_+ = 0.119 \pm 0.090 \hbox{(stat.)} \pm 0.053 \hbox{(syst.)}$, which is consistent at the 30% C.L. with the standard model.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00184815
Contributor : Dominique Girod Connect in order to contact the contributor
Submitted on : Friday, November 2, 2007 - 9:09:03 AM
Last modification on : Sunday, June 26, 2022 - 11:47:38 AM

### Citation

V.M. Abazov, B. Abbott, M. Abolins, B.S. Acharya, M. Adams, et al.. Model-independent measurement of the W boson helicity in top quark decays. Physical Review Letters, American Physical Society, 2008, 100, pp.062004. ⟨10.1103/PhysRevLett.100.062004⟩. ⟨in2p3-00184815⟩

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