Probing the tau electric dipole moment at the BEPC-II collider

We investigate the prospects of the search for a nonzero tau EDM form factor d(tau) (s) in tau-pair production by e(+) e(-) collisions at BEPC-II collider energies. We compute the expectation values and covariances of simple and optimal CP-odd observables for tau-pair production at root s = 4.18 and 4.95 GeV with subsequent decays of tau(+/-) into major leptonic or semihadronic modes. For the tau decays to two pions and three charged pions, we take the full kinematic information of the hadronic system into account. Applying cuts and using realistic assumptions on the eventually attainable integrated luminosities at these energies, L(4.18) = 3 x 10(4) pb(-1) and L(4.95) = 10(4) pb(-1), respectively, we find the following. By taking into account purely semihadronic and semihadronic-leptonic tau(+) tau(-) decays one can achieve with optimal CP-odd observables the 1 s.d. sensitivities delta Red(tau) = 4.5 x 10(-18) e cm (5.3 x 10(-18) e cm) and delta Imd(tau) = 2.2 x 10(-18) e cm (2.7 x 10(-18) e cm) at root s = 4.18 GeV (4.95 GeV).