Sensitivity study of searching for $$\tau ^- \rightarrow \gamma \mu ^-$$τ-→γμ- at HIEPA

The charged lepton flavor violation process is a clean and sensitive probe of new physics beyond the Standard Model. A sensitivity study is performed to the process τ^-→γμ^- based on a 3 fb^-1 inclusive Monte Carlo sample of e⁺e^- collisions at a center-of-mass energy of4.26 or 4.6 Ge V, in the framework of the BESIII software system. The 90 % confidence level upper limits on B（τ^-→γμ^-） are estimated assuming no signal is produced. We also obtain the sensitivity on B（τ^-→γμ^-） as a function of the integrated luminosity, to serve as a reference for the HIEPA being proposed in China. It is found that 6.34 ab^-1 are needed to reach the current best upper limit of 4:4 10^-8 and about 2510 ab^-1 are needed to reach a sensitivity of 10^-9 if the detector design is similar to that of BESIII.