Determination of the Pseudoscalar Decay Constant fDs+ via Ds+→μ+νμ

Résumé fourni par la source

Using a $3.19\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample collected at an ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy of ${E}_{\mathrm{cm}}=4.178\text{ }\text{ }\mathrm{GeV}$ with the BESIII detector, we measure the branching fraction of the leptonic decay ${D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ to be ${\mathcal{B}}_{{D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}=(5.49\ifmmode\pm\else\textpm\fi{}0.1{6}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.1{5}_{\text{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. Combining our branching fraction with the masses of the ${D}_{s}^{+}$ and ${\ensuremath{\mu}}^{+}$ and the lifetime of the ${D}_{s}^{+}$, we determine ${f}_{{D}_{s}^{+}}|{V}_{cs}|=246.2\ifmmode\pm\else\textpm\fi{}3.{6}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}3.{5}_{\text{syst}}\text{ }\text{ }\mathrm{MeV}$. Using the $c\ensuremath{\rightarrow}s$ quark mixing matrix element $|{V}_{cs}|$ determined from a global standard model fit, we evaluate the ${D}_{s}^{+}$ decay constant ${f}_{{D}_{s}^{+}}=252.9\ifmmode\pm\else\textpm\fi{}3.{7}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}3.{6}_{\text{syst}}\text{ }\text{ }\mathrm{MeV}$. Alternatively, using the value of ${f}_{{D}_{s}^{+}}$ calculated by lattice quantum chromodynamics, we find $|{V}_{cs}|=0.985\ifmmode\pm\else\textpm\fi{}0.01{4}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.01{4}_{\text{syst}}$. These values of ${\mathcal{B}}_{{D}_{s}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}$, ${f}_{{D}_{s}^{+}}|{V}_{cs}|$, ${f}_{{D}_{s}^{+}}$ and $|{V}_{cs}|$ are each the most precise results to date.

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