Measurements of e+e−→ηcπ+π−π0 , ηcπ+π− , and ηcπ0γ at s from 4.18 to 4.60 GeV, and search for a Zc state close to the DD¯ threshold decaying to ηcπ at s=4.23 GeV

Le résumé fourni par la source

We study ${\ensuremath{\eta}}_{\mathrm{c}}$ production at center-of-mass energies $\sqrt{s}$ from 4.18 to 4.60 GeV in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data collected with the BESIII detector operating at the BEPCII storage ring, corresponding to $7.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity. We measure the cross sections of the three different exclusive reactions ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{\mathrm{c}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{\mathrm{c}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{\mathrm{c}}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$. We find significant ${\ensuremath{\eta}}_{\mathrm{c}}$ production in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{\mathrm{c}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ at $\sqrt{s}$ of 4.23 GeV and 4.26 GeV and observe a significant energy-dependent Born cross section that we measure to be consistent with the production via the intermediate $Y(4260)$ resonance. In addition, we perform a search for a charmoniumlike ${Z}_{\mathrm{c}}$ state close to the $D\overline{D}$ threshold that decays to ${\ensuremath{\eta}}_{\mathrm{c}}\ensuremath{\pi}$, involving ground state charmonium, and observe no signal. Corresponding upper limits on the cross section of ${\ensuremath{\eta}}_{\mathrm{c}}$ and ${Z}_{\mathrm{c}}$ production are provided, where the yields are not found to be significant.

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