We report measurements of the polarization of W bosons
from top-quark decays using 2.7 fb-1 of p anti-p collisions collected
by the CDF II detector. Assuming a top-quark mass of 175 GeV/c2,
three measurements are performed. A simultaneous measurement of the
fraction of longitudinal (f_0) and right-handed (f_+) W bosons yields
the model-independent results f_0 0.88 +/- 0.11(stat) +/- 0.06(syst) and
f_+ ÿ0.15 +/- 0.07(stat) +/- 0.06(syst) with a correlation coefficient
of -0.59. A measurement of f_0 (f_+) constraining f_+ (f_0) to its
standard model value of 0.0 (0.7) yields f_0 ð.70 +/- 0.07(stat) +/-
0.04(syst) (f_+ ÿ0.01 +/- 0.02(stat) +/- 0.05(syst)). All these results
are consistent with standard model expectations.
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Updated: Monday, 2010 July 26 16:21:08 CDT automatically from input from Carol Picciolo