Model-independent study on the anomalous $\tau \bar{\tau }\gamma$ couplings at the ILC

Abstract

The potential of the process $\gamma \gamma \to \tau \bar{\tau }\gamma$ 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 $\widetilde{d_{\tau }}$ 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 $|\widetilde{d_{\tau }}|<3.5969\times 10^{-18}$ $ecm$, 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.

23 pages, 15 figures, 8 tables