We present a measurement of the coefficient alpha_2 of the
leptonic polar-angle distribution from W boson decays, as a function of the
W transverse momentum. The measurement uses an 80 +/- 4 pb-1 sample of
p anti-p collisions at s**(1/2) = 1.8 TeV collected by the CDF detector and
includes data from both the W --> e + nu and W --> mu + nu decay channels. We
fit the W boson transverse mass distribution to a set of templates from a
Monte Carlo event generator and detector simulation in several ranges of the
W transverse momentum. The measurement agrees with the Standard Model
expectation, whereby the ratio of longitudinally to transversely polarized W
bosons, in the Collins-Soper W rest frame, increases with the W transverse
momentum at a rate of approximately 15% per 10 GeV/c.
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Updated: Wednesday, 2004 September 15 10:06:52 CDT automatically from input from "Carol I. Picciolo"