A search for the electric dipole moment of the tau-lepton

Using the ARGUS detector at the e(+)e(-) storage ring DORIS II, we have sea rched for the real and imaginary part of the electric dipole formfactor d(t au) of the tau lepton in the production of tau pairs at q(2)=100GeV(2). Thi s is the first direct measurement of this CP violating formfactor. We appli ed the method of optimised observables which takes into account all availab le information on the observed tau decay products. No evidence for CP viola tion was found, and we derive the following results: Re(d(tau)) = (1.6 +/- 1.9) . 10(-16) e cm and Im(d(tau)) = (-0.2 +/- 0.8) . 10(-16) e cm, where s tatistical and systematic errors have been combined. (C) 2000 Elsevier Scie nce B.V. All rights reserved.