XIXth Workshop on High Energy Spin Physics dedicated to 90th anniversary of A.V. Efremov birth

Manifestation of the electric dipole moment in the decays of τ leptons produced in e+e− annihilation

6 Sept 2023, 10:45

25m

BLTP Conference Hall (JINR)

Plenary

Speaker

Obraztsov, Ivan (Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia and Novosibirsk State University, 630090, Novosibirsk, Russia)

Description

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

Presentation materials

Manifestation of the electric dipole moment in the decays of τ leptons produced in e+e− annihilation

Obraztsov Ivan DSPIN 2023.pdf