An improved search for the electric dipole moment of the tau lepton

Abstract

We report a measurement of the electric dipole moment of the tau lepton (d(tau)) using an 833 fb(-1) data sample collected near the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. Using an optimal observable method, we obtain the real and imaginary parts of d(tau) as Re(d(tau)) = (-0.62 +/- 0.63) x 10(-17) ecm and Im(d(tau)) = (-0.40 +/- 0.32) x 10(-17) ecm, respectively. These results are consistent with null electric dipole moment at the present level of experimental sensitivity and improve the sensitivity by about a factor of three.