An improved search for the electric dipole moment of the $\ddot{I}„$ lepton

Abstract

We report a measurement of the electric dipole moment of the $\ddot{I}„$ lepton ($d_{\ddot{I}}„$) using an 833~fb${}^{-1}$ data sample collected near the $\hat{I}\yen (4S)$ 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 $d_{\ddot{I}}„$ as $\mathrm{Re}(d_{\ddot{I}}„)=(-0.62\pm 0.63)\times 10^{-17}e\mathrm{cm}$ and $\mathrm{Im}(d_{\ddot{I}}„)=(-0.40\pm 0.32)\times 10^{-17}e\mathrm{cm}$, 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.

10 pages, 5 figures