Prospects of CKM elements $|V_{cs}|$ and decay constant $f_{D_s^{+}}$ in $D_s^{+}\to {\mu }^{+}{\nu }_{\mu }$ decay at STCF

Abstract

We report a feasibility study of pure leptonic decay $D_s^{+}\to {\mu }^{+}{\nu }_{\mu }$ 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 $c\to s$ 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. The unprecedented precision to be achieved at STCF will provide a precise calibration of QCD and rigorous test of Standard Model.

arXiv comment8pages, 7 figures