Testing V-A in top decay at CDF at squareroot s = 1.8 TeV

The structure of the tbW vertex can be probed by measuring the polarization of the W in t → W + b → l + v + b. The invariant mass of the lepton and b quark measures the W decay angle which in turn allows a comparison with polarizations expected from a V-A and V+A tbW vertex. We measure the fraction by rate of Ws produced with a V+A coupling in lieu of the Standard Model V-A to be fV+A = -0.21-0.24+0.42(stat) ± 0.21(sys). We assign a limit of fV+A < 0.80 (at) 95% CL. By combining this result with a complementary observable in the same data, we assign a limit of fV+A < 0.61 (at) 95% CL. From this CDF Run I preliminary result, we find no evidence for a non-standard Model tbW vertex