Measurement of the anomalous magnetic and electric dipole moments of the tau lepton

Abstract We analyse e + e − → ττγ events using 100 pb −1 of data collected by the L3 experiment during the 1991-1995 LEP runs at the Z pole. From the energy of the photons and their isolation from the tau decay products, we determine the anomalous magnetic and electric dipole moments of the tau to be, respectively: a τ =0.004±0.027±0.023; d τ =(0.0±1.5±1.3)×10 −16 e· cm . This is a direct measurement of these τ form factors at q 2 =0.