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

The BELLE Collaboration, K. Inami, K. Hayasaka, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, V. Aulchenko, T. Aushev, R. Ayad, V. Babu, S. Bahinipati (+177 others)
We report a measurement of the electric dipole moment of the τ lepton (dτ) using an 833 fb$^{-1}$ data sample collected near the Υ($_{4}$S) 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 dτ as Re(d$_{τ}$) = (−0.62 ± 0.63) × 10$^{-17}$ ecm and Im(d$_{τ}$) = (−0.40 ± 0.32) × 10$^{-17}$ ecm, respectively. These results are consistent with null electric dipole moment at the
more » ... t level of experimental sensitivity and improve the sensitivity by about a factor of three.
doi:10.5445/ir/1000146025 fatcat:mkboonqeb5adldi4cnouchshqm