Tau weak dipole moments from azimuthal asymmetries

Abstract

We show that transverse and normal single-$tau$ polarization of $tau$ pairs produced at $e^{+}$ $e^{-}$ unpolarized collisions, at the $Z$ peak, are sensitive to weak (magnetic and electric) dipole moments of the $tau$. We also show how these components of the $\tau$ polarization are accessible by measuring appropriate azimuthal asymmetries in the angular distribution of its decay products. Sensitivities of the order of $10^{-18}$ $e\cdot cm$, for the weak-electric dipole moment, and $10^{-4}$ ($10^{-3}$), for the real (imaginary) part of the weak-magnetic dipole moment of $\tau$, may be achieved. Compatible bounds are also presented from spin-spin correlated asymmetries.

Comments: Talk given at the TAU'98 Workshop, September 1998, Santander, Spain. 8 pages, 2 figures