Measurement of helicity parameters in top quark decay

Ch.A. Nelson, A.M. Cohen
1999 European Physical Journal C: Particles and Fields  
The standard model(SM) predicts only a g_V-A coupling in t → 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 → 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 Λ_S+P∼ -35 GeV, g_V-A + g_f_M + f_E with Λ_f_M + f_E∼
more » ... 53 GeV, and an arbitrary sign-flip in the b_L amplitudes A_X (λ_b = - 1/2) = - A_V-A (λ_b = - 1/2). These ambiguities are analyzed so that they might be partially resolved when experiments resume at the Fermilab Tevatron.
doi:10.1007/s100520050474 fatcat:q3m5ynrkhba3zgjhkylhtpcaqe