How to search for an electric dipole form factor of the τ lepton at a τ-charm factory

We investigate some CP-odd correlations which can be used to search for an electric dipole form factor dτ(s) of the τ in the reaction e+e- → τ+τ - at c.m. energies √s relevant for a τ-charm factory. These observables require measurement of the τ polarizations. Using the channel e+e- → π+ ντπ-ντ one should be able to measure dτ at √s = 4 GeV with an accuracy δ(dτ) ≅ 2.5 x 10-16e cm, assuming the production of 107 τ pairs. The same accuracy can be reached with 106 τ pairs at √s = 10 GeV, the typical c.m. energy of a B-factory. 8 refs., 2 figs., 1 tab