Evidence for B+→hcK+ and observation of ηc(2S)→pp¯π+π−

Le résumé fourni par la source

A search for the decays ${B}^{+}\ensuremath{\rightarrow}{h}_{c}{K}^{+}$ and ${B}^{0}\ensuremath{\rightarrow}{h}_{c}{K}_{S}^{0}$ is performed. Evidence for the decay ${B}^{+}\ensuremath{\rightarrow}{h}_{c}{K}^{+}$ is found; its significance is $4.8\ensuremath{\sigma}$. No evidence is found for ${B}^{0}\ensuremath{\rightarrow}{h}_{c}{K}_{S}^{0}$. The branching fraction for ${B}^{+}\ensuremath{\rightarrow}{h}_{c}{K}^{+}$ is measured to be $({3.7}_{\ensuremath{-}0.9}^{+1.0}{\text{ }}_{\ensuremath{-}0.8}^{+0.8})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$; the upper limit for the ${B}^{0}\ensuremath{\rightarrow}{h}_{c}{K}_{S}^{0}$ branching fraction is $1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at 90% C.L. In addition, a study of the $p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant mass distribution in the channel ${B}^{+}\ensuremath{\rightarrow}(p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}){K}^{+}$ results in the first observation of the decay ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}p\overline{p}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ with $12.1\ensuremath{\sigma}$ significance. The analysis is based on the $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample collected by the Belle detector at the asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider KEKB at the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance.

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