Measurement of the Helicity of W Bosons in Top-Quark Decays

الأصل · EN

We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F₀ and F+, using approximately 200 pb⁻¹ of pp collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t→ Wb → ℓνb (where ℓ=e or μ), and the transverse momentum of the charged lepton. We find F₀=0.74⁺⁰.²²₋₀.₃₄, and F+<0.27 at the 95% confidence level. These measurements are in agreement with the standard model predictions.