  The Lorentz structure of the tau lepton's charged-current can almost be
completely determined by use of stage-two spin-correlation functions for the
$\{\rho ^{-},\rho ^{+}\}$ and $\{a_1^{-},a_1^{+}\}$ decay modes It is possible
to test for a ``(V-A) + something'' structure in the ${J^{Charged}}_{Lepton}$
current, so as to bound the scales $\Lambda$ for ``new physics" such as arising
from tau weak magnetism, weak electricity, and/or second-class currents.

High Energy Physics - Phenomenology