Observation of B+→pΛ¯K+K− and B+→p¯ΛK+K+

Le résumé fourni par la source

We report the study of ${B}^{+}\ensuremath{\rightarrow}p\overline{\mathrm{\ensuremath{\Lambda}}}{K}^{+}{K}^{\ensuremath{-}}$ and ${B}^{+}\ensuremath{\rightarrow}\overline{p}\mathrm{\ensuremath{\Lambda}}{K}^{+}{K}^{+}$ decays using a $772\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }B\overline{B}$ pair data sample recorded on the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance with the Belle detector at KEKB. The following branching fractions are measured: $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}p\overline{\mathrm{\ensuremath{\Lambda}}}{K}^{+}{K}^{\ensuremath{-}})=(4.1{0}_{\ensuremath{-}0.43}^{+0.45}\ifmmode\pm\else\textpm\fi{}0.50)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}\overline{p}\mathrm{\ensuremath{\Lambda}}{K}^{+}{K}^{+})=\phantom{\rule{0ex}{0ex}}(3.7{0}_{\ensuremath{-}0.37}^{+0.39}\ifmmode\pm\else\textpm\fi{}0.44)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}p\overline{\mathrm{\ensuremath{\Lambda}}}{K}^{\ensuremath{-}}+\mathrm{c}.\mathrm{c}.)=({2.83}_{\ensuremath{-}0.34}^{+0.36}\ifmmode\pm\else\textpm\fi{}0.35)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}p\overline{\mathrm{\ensuremath{\Lambda}}}\ensuremath{\phi})=\phantom{\rule{0ex}{0ex}}(\text{ }7.95\ifmmode\pm\else\textpm\fi{}2.09\ifmmode\pm\else\textpm\fi{}0.77)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also find evidence for $\mathcal{B}({\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}(1520)\overline{\mathrm{\ensuremath{\Lambda}}}+\mathrm{c}.\mathrm{c}.)=(3.48\ifmmode\pm\else\textpm\fi{}1.48\ifmmode\pm\else\textpm\fi{}0.46)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}(1520)\overline{\mathrm{\ensuremath{\Lambda}}}{K}^{+})=(\text{ }2.23\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.63\ifmmode\pm\else\textpm\fi{}0.25)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. No significant signals are found for $J/\ensuremath{\psi}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}(1520)\overline{\mathrm{\ensuremath{\Lambda}}}+\mathrm{c}.\mathrm{c}.$ and ${B}^{+}\ensuremath{\rightarrow}\phantom{\rule{0ex}{0ex}}\overline{\mathrm{\ensuremath{\Lambda}}}(1520)\mathrm{\ensuremath{\Lambda}}{K}^{+}$; we set the 90% confidence level upper limits on their decay branching fractions as $<1.80\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $<2.08\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, respectively.

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