Observation of a structure at 1.84 GeV/c2 in the 3(π+π−) mass spectrum in J/ψ→γ3(π+π−) decays

Le résumé fourni par la source

With a sample of $225.3\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $J/\ensuremath{\psi}$ events taken with the BESIII detector, the decay $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ is analyzed. A structure at $1.84\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ is observed in the $3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ invariant mass spectrum with a statistical significance of $7.6\ensuremath{\sigma}$. The mass and width are measured to be $M=1842.2\ifmmode\pm\else\textpm\fi{}{4.2}_{\ensuremath{-}2.6}^{+7.1}\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $\ensuremath{\Gamma}=83\ifmmode\pm\else\textpm\fi{}14\ifmmode\pm\else\textpm\fi{}11\text{ }\text{ }\mathrm{MeV}$. The product branching fraction is determined to be $B(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}X(1840))\ifmmode\times\else\texttimes\fi{}B(X(1840)\ensuremath{\rightarrow}3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}))=(2.44\ifmmode\pm\else\textpm\fi{}{0.36}_{\ensuremath{-}0.74}^{+0.60})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. No ${\ensuremath{\eta}}^{\ensuremath{'}}$ signals are observed in the $3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ invariant mass spectrum, and the upper limit of the branching fraction for the decay ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$ is set to be $3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at a 90% confidence level.

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