Evidence of ϒ(1S)→J/ψ+χc1 and search for double-charmonium production in ϒ(1S) and ϒ(2S) decays

Le résumé fourni par la source

Using data samples of $102\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\mathrm{\ensuremath{\Upsilon}}(1S)$ and $158\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\mathrm{\ensuremath{\Upsilon}}(2S)$ events collected with the Belle detector, a first experimental search has been made for double-charmonium production in the exclusive decays $\mathrm{\ensuremath{\Upsilon}}(1S,2S)\ensuremath{\rightarrow}J/\ensuremath{\psi}({\ensuremath{\psi}}^{\ensuremath{'}})+X$, where $X={\ensuremath{\eta}}_{c}$, ${\ensuremath{\chi}}_{cJ}(J=0,1,2)$, ${\ensuremath{\eta}}_{c}(2S)$, $X(3940)$, and $X(4160)$. No significant signal is observed in the spectra of the mass recoiling against the reconstructed $J/\ensuremath{\psi}$ or ${\ensuremath{\psi}}^{\ensuremath{'}}$ except for the evidence of ${\ensuremath{\chi}}_{c1}$ production with a significance of $4.6\ensuremath{\sigma}$ for $\mathrm{\ensuremath{\Upsilon}}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+{\ensuremath{\chi}}_{c1}$. The measured branching fraction $\mathcal{B}(\mathrm{\ensuremath{\Upsilon}}(1S)\ensuremath{\rightarrow}J/\ensuremath{\psi}+{\ensuremath{\chi}}_{c1})$ is $[3.90\ifmmode\pm\else\textpm\fi{}1.21(\text{stat})\ifmmode\pm\else\textpm\fi{}0.23(\text{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. The 90% C.L. upper limits on the branching fractions of the other modes having a significance of less than $3\ensuremath{\sigma}$ are determined. These results are consistent with theoretical calculations using the nonrelativistic QCD factorization approach.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.