Speaker
Description
We report a feasibility study of pure leptonic decay $D_s^{+}\to\ell^+\nu_{\ell}$ by using a fast simulation software package at STCF. With an expected luminosity of 1 ab$^{-1}$ collected at STCF at a center-of-mass energy of 4.009 GeV, the statistical sensitivity of the branching fraction is determined to be 0.3%. Combining this result with the c → s quark mixing matrix $|V_{cs}|$ element determined from the current global Standard Model fit, the statistical sensitivity of $D_s^{+}$ decay constant, $f_{D_s^{+}}$, is estimated to be 0.2%. Alternatively, combining the current results of $f_{D_s^{+}}$ calculated by lattice QCD, the statistical sensitivity of $|V_{cs}|$ is determined to be 0.2%, which helps probe possible new physics beyond. The unprecedented precision to be achieved at STCF will provide a precise calibration of QCD and rigorous test of Standard Model.
