Improved measurement of the electroweak penguin process B→Xsℓ+ℓ−

Le résumé fourni par la source

We present an improved measurement of the branching fraction for the electroweak penguin process $B\ensuremath{\rightarrow}{X}_{s}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$, where $\ensuremath{\ell}$ is an electron or a muon and ${X}_{s}$ is a hadronic system containing an $s$-quark. The measurement is based on a sample of $152\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}B\overline{B}$ events collected with the Belle detector at the KEKB energy asymmetric ${e}^{+}{e}^{\ensuremath{-}}$ collider. The ${X}_{s}$ hadronic system is reconstructed from one ${K}^{\ifmmode\pm\else\textpm\fi{}}$ or ${K}_{\mathrm{S}}^{0}$ and up to four pions, where at most one pion can be neutral. Averaging over both lepton flavors, the inclusive branching fraction is measured to be $\mathcal{B}(B\ensuremath{\rightarrow}{X}_{s}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}})=(4.11\ifmmode\pm\else\textpm\fi{}0.83(\mathrm{stat}{)}_{\ensuremath{-}0.81}^{+0.85}(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for ${M}_{{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}}>0.2\text{ }\mathrm{GeV}/{c}^{2}$.

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