On measurement of helicity parameters in top quark decay

To enable an evaluation of future measurements of the helicity parameters for decay in regard to violation, this paper considers the effects of an additional pure-imaginary coupling, or , associated with a specific, single additional Lorentz structure, . Sizable violation signatures can occur for low-effective mass scales (), but in most cases can be more simply excluded by precision measurement of the probabilities and . Signatures for excluding the presence of violation associated with the two dynamical phase-type ambiguities are investigated. Received: 10 July 2000 / Published online: 8 September 2000