Prospects of CKM elements |V_{cs}| and decay constant f_{D_{s}^+} in D_s^+rightarrow mu ^+nu _mu decay at STCF

Abstract

We report a feasibility study of pure leptonic decay D_s^+rightarrow mu ^+nu _mu by using a fast simulation software package at STCF. With an expected luminosity of 1~mathrm {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 rightarrow 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.