Tests at a Tau/Charm Factory with Longitudinally Polarized Beams

Abstract

In a recent paper, eight semileptonic parameters were defined to specify the most general Lorentz-invariant spin correlation functions for tau semileptonic decays. The parameters were physically defined in terms of tau-decay partial-width intensities for polarized final states. This paper studies how these parameters can be simply measured at a tau/charm factory with longitudinally polarized beams without using spin-correlation techniques. Thereby the parameters can also be used to bound the effective-mass scales $ \Lambda $ for ``new physics" such as arising from lepton compositeness, leptonic CP violation, leptonic T violation, tau weak magnetism, weak electricity, and/or second-class currents.