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.