We report an upper limit on the fraction of V + A current, f_V+A,
in top quark decays, using approximately 700 pb-1 of p anti-p collisions at
s**(1/2) = 1.96 TeV acquired by the upgraded Collider Detector at Fermilab.
For the decay t --> Wb --> l nu b (where l = e or mu), the invariant mass of
the charged lepton and the bottom quark jet is sensitive to the polarization
of the W boson. We determine f_V+A = -0.06 +/- 0.25 given a top quark mass
of 175 GeV/c2. We set an upper limit on f_V+A of 0.29 at the 95%
confidence level, which represents an improvement by a factor of two on the
previous best direct limit.
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Updated: Friday, 2007 February 16 15:54:31 CST automatically from input from Carol Picciolo