Prediction for CP Violation via Electric Dipole Moment of $\tau$ Lepton in $\gamma \gamma \to {\tau }^{+}{\tau }^{-}$ Process at CLIC

Pair production of tau leptons in two photon collision ${\gamma\gamma \to \tau^{+}\tau}^{-}$ is studied at CLIC to test CP violating QED couplings of tau leptons. CP violating effects are investigated using tau pair spin correlations which are observed through the hadronic decay of each $\tau$ into $\pi \nu$. Competitive bounds with previous works on the electric dipole moment from CP odd terms have been obtained.