Azimuthal asymmetries at the Z peak

The τ+τ- produced at the Z peak provide interesting information through the expectation values of their polarization. Besides the longitudinal polarization, there are two spin correlations which involve the transverse (within the production plane) and normal (to the production plane) polarization components of both τ-leptons. The transverse-normal spin correlation is an observable odd under time reversal. It was found that each of these spin correlations leads to an associated azimuthal asymmetry in the angular distribution of the τ+ and τ- decay products, which can be measured without reconstructing the τ-vertex. (author) 7 refs., 2 figs., 1 tab