Measurement of w-boson polarization in top-quark decay in pp̄ collisions at √s=1.96TeV

We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb{sup -1} of pp collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c{sup 2}, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f{sub 0}) and right-handed (f{sub +}) W bosons yields the model-independent results f{sub 0}=0.88{+-}0.11(stat){+-}0.06(syst) and f{sub +}=-0.15{+-}0.07(stat){+-}0.06(syst) with a correlation coefficient of -0.59. A measurement of f{sub 0}[f{sub +}] constraining f{sub +}[f{sub 0}] to its standard model value of 0.0 [0.7] yields f{sub 0}=0.70{+-}0.07(stat){+-}0.04(syst)[f{sub +}=-0.01{+-}0.02(stat){+-}0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f{sub 0} for both the model-independent and model-dependent determinations.