Manifestation of the electric dipole moment in the decays of $\tau$ leptons produced in $e^+e^-$ annihilation

Abstract

$\mbox{CP}$-odd asymmetries in the processes $e^+e^-\rightarrow \tau^+\pi^-\nu_\tau$, $e^+e^-\rightarrow \pi^+\tau^-\bar\nu_ \tau$, $e^+e^-\rightarrow \tau^+\rho^-\nu_\tau$, $e^+e^-\rightarrow \rho^+\tau^-\bar\nu_\tau $, $e^+e^-\to \tau^+e^-\nu_\tau{\bar\nu}_e\,,\,$ and $\,e^+e^-\to \tau^-e^+\nu_e{\bar\nu}_\tau$ are investigated with account for longitudinal polarization of electron (or positron) beam. These asymmetries is a manifestation of electric dipole form factor $F_3^\tau\equiv b$ in the $\gamma\tau^+\tau^-$ vertex. It is shown that, to measure $\mbox{Im}\,b$ in the specified processes, polarization is not needed, while to measure $\mbox{Re}\,b$ it is required. The processes $e^+e^-\to \pi^+\pi^-\nu_\tau{\bar\nu}_\tau$, $e^+e^-\to e^+e^-\nu_\tau{\bar\nu}_\tau\nu_e\bar\nu_e$, $e^+e^-\to \mu^+\mu^-\nu_\tau{\bar\nu}_\tau\nu_\mu\bar\nu_\mu$, $e^+e^-\to \mu^+e^-\nu_\tau{\bar\nu}_\tau\nu_\mu\bar\nu_e$, and $e^+e^-\to \mu^-e^+\nu_\tau{\bar\nu}_\tau\nu_e\bar\nu_\mu$ are also discussed for the case of unpolarized electron and positron beams. In the latter cases it is possible to measure $\mbox{Re}\,b$ using the differential cross section over momenta of both registered particles.