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Measurement of the W boson helicity in top quark decay at D0.

Research output: Contribution to journalJournal articlepeer-review

<mark>Journal publication date</mark>2007
<mark>Journal</mark>Physical Review D
Pages (from-to)031102
Publication StatusPublished
<mark>Original language</mark>English


We present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of t[overline t] events in the [script-l]+jets and dilepton decay channels corresponding to an integrated luminosity of 370 pb-1 collected by the D0 detector at the Fermilab Tevatron p[overline p] Collider at sqrt(s)=1.96 TeV. We reconstruct the decay angle theta* for each lepton. By comparing the costheta* distribution from the data with that for the expected background and signal for various values of f+ (where we assume that the fraction of longitudinally-polarized W bosons has the standard model value of 0.70), we find f+=0.056±0.080(stat)±0.057(syst) (f+<0.23 at 95% C.L.), consistent with the standard model prediction of f+=3.6×10-4.