Prospects of CKM elements |Vcs| and decay constant fDs+ in Ds+→μ+νμ decay at STCF.

We report a feasibility study of pure leptonic decay D s + → μ + ν μ 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 element | V cs | 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 Standard Model. The unprecedented precision to be achieved at STCF will provide a precise calibration of QCD and rigorous test of Standard Model. [ABSTRACT FROM AUTHOR]