Testing for New Couplings in Top Quark Decay

Abstract

Tests of the Lorentz structure of t --> W b decay will be carried out at the Tevatron, and later at the LHC and at a NLC. To quantitatively assay future measurements of competing observables, we consider the (V-A) coupling values of the helicity decay parameters versus "(V-A) + Single Additional Lorentz Structures". Three phase-type ambiguities exist, but measurement of the sign of the large interference between the W boson longitudinal/transverse amplitudes could exclude the two due dynamically to additional (S+P) and (f_M + f_E) couplings. Sizable T-violation signatures can occur for low-effective mass scales, < 320 GeV, but in most cases can be more simply excluded by 10% precision measurement of the probabilities P(W_L) and P(b_L). Signatures for the presence of T-violation associated with the dynamical phase-type ambiguities, CP-violation signatures, and Lambda_b polarimetry are also discussed.