Model-independent study on the anomalous $τ\barτγ$ couplings at the ILC (2104.01003v1)

Abstract: The potential of the process $\gamma \gamma \rightarrow \tau \bar{\tau}\gamma$ is examined in a model-independent way using the effective Lagrangian approach for the ILC which is designed with standard configurations of 0.25 TeV/2000 fb$^{-1}$, 0.35 TeV/200 fb$^{-1}$ and 0.5 TeV/4000 fb$^{-1}$. The limits obtained for $\tilde{a}{\tau}$ and $\tilde{{d}{\tau}}$ parameters defining the anomalous $\tau \bar{\tau}\gamma$ couplings at $95\%$ confidence level and systematic uncertainties of $\delta_{sys}=0,5,10 \%$ are compared with the experimental results. The best limits obtained without systematic error on the anomalous couplings are $-0.00082<\tilde{a}{\tau}<0.00050$ and $|\tilde{{d}{\tau}}|<3.5969 \times 10^{-18}$ $e\,cm$, respectively. Thus, our results show that $\gamma \gamma$ collisions at the ILC lead to a remarkable improvement in the existing experimental limits on the anomalous magnetic and electric dipole moments of the tau lepton.