Higgs to $\tau \tau$ analysis in the future $e^{+}{e}^{-}$ Higgs factories

The Circular Electron Positron Collider and International Linear Collider are two electron positron Higgs factories. They are designed to operate at center-of-mass energy of 240 and 250 GeV and accumulate 5.6 and 2 $a{b}^{-1}$ of integrated luminosity. Using CEPC official samples, the signal strength for Higgs to $\tau \tau$ events are analyzed. The combined accuracy of the signal strength for $H\to \tau \tau$ at CEPC achieves 0.8%. Extrapolating this analysis to the ILC setup, we conclude the ILC can reach a relative accuracy of 1.1% or 1.2%, corresponding to two benchmark settings of the beam polarization.