Observation of Resonance Structures in e+e−→π+π−ψ2(3823) and Mass Measurement of ψ2(3823)

Le résumé fourni par la source

Using a data sample corresponding to an integrated luminosity of $11.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\psi}}_{2}(3823)$ cross section and the branching fraction $\mathcal{B}[{\ensuremath{\psi}}_{2}(3823)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\chi}}_{c1}]$. For the first time, resonance structure is observed in the cross section line shape of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\psi}}_{2}(3823)$ with significances exceeding $5\ensuremath{\sigma}$. A fit to data with two coherent Breit-Wigner resonances modeling the $\sqrt{s}$-dependent cross section yields $M({R}_{1})=4406.9\ifmmode\pm\else\textpm\fi{}17.2\ifmmode\pm\else\textpm\fi{}4.5\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, $\mathrm{\ensuremath{\Gamma}}({R}_{1})=128.1\ifmmode\pm\else\textpm\fi{}37.2\ifmmode\pm\else\textpm\fi{}2.3\text{ }\text{ }\mathrm{MeV}$, and $M({R}_{2})=\phantom{\rule{0ex}{0ex}}4647.9\ifmmode\pm\else\textpm\fi{}8.6\ifmmode\pm\else\textpm\fi{}0.8\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, $\mathrm{\ensuremath{\Gamma}}({R}_{2})=33.1\ifmmode\pm\else\textpm\fi{}18.6\ifmmode\pm\else\textpm\fi{}4.1\text{ }\text{ }\mathrm{MeV}$. Though weakly disfavored by the data, a single resonance with $M(R)=4417.5\ifmmode\pm\else\textpm\fi{}26.2\ifmmode\pm\else\textpm\fi{}3.5\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, $\mathrm{\ensuremath{\Gamma}}(R)=245\ifmmode\pm\else\textpm\fi{}48\ifmmode\pm\else\textpm\fi{}13\text{ }\text{ }\mathrm{MeV}$ is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the ${\ensuremath{\psi}}_{2}(3823)$ state is measured as $(3823.12\ifmmode\pm\else\textpm\fi{}0.43\ifmmode\pm\else\textpm\fi{}0.13)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, which is the most precise measurement to date.

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