Search for anomalous weak dipole moments of the τ lepton

The anomalous weak dipole moments of the τ lepton are measured in a data sample collected by ALEPH from 1990 to 1995 corresponding to an integrated luminosity of 155 pb-1. Tau leptons produced in the reaction e+e-→τ+τ- at energies close to the Z mass are studied using their semileptonic decays to π,ρ,a1→π2π0 or a1→3π. The real and imaginary components of both the anomalous weak magnetic dipole moment and the CP-violating anomalous weak electric dipole moment, Reμτ, Imμτ, Redτ and Imdτ, are measured simultaneously by means of a likelihood fit built from the full differential cross section. No evidence of new physics is found. The following bounds are obtained (95% CL): vertical stroke Reμτ vertical stroke <1.14 x 10-3, vertical stroke Imμτ vertical stroke < 2.65 x 10-3, vertical stroke Re dτ vertical stroke < 0.91 x 10-3, and vertical stroke Im dτ vertical stroke < 2.01 x 10-3. (orig.)