Measurement of Helicity Parameters in Top Quark Decay
  The standard model(SM) predicts only a $g_{V-A}$ coupling in $t \to W^+ b$ decay. However, if additional Lorentz structures exist, they can manifest themselves in high energy processes such as this via non-SM values of the helicity parameters describing $t \to W^+ b$. Plots and tables of the values of these helicity parameters are obtained for various coupling strengths. Three phase-type ambiguities are uncovered: $g_{V-A} + g_{S+P}$ with effective-mass scale $\Lambda_{S+P} \sim -35 GeV, g_{V-A} + g_{f_M + f_E}$ with $\Lambda_{f_M + f_E} \sim 53 GeV$, and an arbitrary sign-flip in the $b_L$ amplitudes $A_{X} (\lambda_b = - 1/2) = - A_{V-A} (\lambda_b = - 1/2)$. These ambiguities are analyzed so that they might be partially resolved when experiments resume at the Fermilab Tevatron. 
Charles A. Nelson and Andrew M. Cohen