Measurement of the absolute branching fractions for D s − → ℓ − ν ¯ ℓ and extraction of the decay constant f D s

Le résumé fourni par la source

The absolute branching fractions for the decays ${D}_{s}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$, or $\ensuremath{\tau}$) are measured using a data sample corresponding to an integrated luminosity of $521\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected at center-of-mass energies near 10.58 GeV with the BABAR detector at the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ collider at SLAC. The number of ${D}_{s}^{\ensuremath{-}}$ mesons is determined by reconstructing the recoiling system $DKX\ensuremath{\gamma}$ in events of the type ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}DKX{D}_{s}^{*\ensuremath{-}}$, where ${D}_{s}^{*\ensuremath{-}}\ensuremath{\rightarrow}{D}_{s}^{\ensuremath{-}}\ensuremath{\gamma}$ and $X$ represents additional pions from fragmentation. The ${D}_{s}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ events are detected by full or partial reconstruction of the recoiling system $DKX\ensuremath{\gamma}\ensuremath{\ell}$. The branching fraction measurements are combined to determine the ${D}_{s}^{\ensuremath{-}}$ decay constant ${f}_{{D}_{s}}=(258.6\ifmmode\pm\else\textpm\fi{}6.4\ifmmode\pm\else\textpm\fi{}7.5)\text{ }\text{ }\mathrm{MeV}$, where the first uncertainty is statistical and the second is systematic.

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