Model-independent study on the anomalous τ¯τγcouplings at the ILC

Abstract

The potential of the process γγ→τ¯τγis examined in a model-independent way using the effective Lagrangian approach for the International Linear Collider, a proposed electron-positron machine which is designed with standard configurations of 0.25 TeV/2000 fb−1, 0.35 TeV/200 fb−1and 0.5 TeV/4000 fb−1. The limits obtained for the tau lepton’s anomalous magnetic dipole moment ˜ aτand the tau lepton’s anomalous electric dipole moment ˜dτdefining the anomalous τ¯τγcouplings at 95%confidence level and systematic uncertainties of δsys=0, 5, 10%are compared with the experimental results. The best limits obtained with δsys=0%on the anomalous couplings are −0.00082 <˜ aτ<0.00050and |˜dτ| <3.59 ×10−18ecm, respectively. Also, the limits on the anomalous couplings do not improve proportionately to the luminosity due to the systematic error considered here. The reason of this situation is the systematic error which is much bigger than the statistical error. If the systematic error is improved, we expect better limits on the couplings. However, the best limits on the anomalous couplings for the process γγ→τ¯τγwith √s=500GeV, Lint=4000fb−1and δsys=0%can be improved up to 4 times for ˜ aτand 9 times for ˜dτaccording to case with δsys=10%. Our results show that γγcollisions at the ILC give results up to one order of magnitude for ˜ aτand two orders of magnitude for ˜dτbetter than the current experimental limits