Observation of a Neutral Charmoniumlike State Zc(4025)0 in e+e−→(D*D¯*)0π0

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We report a study of the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}({D}^{*}{\overline{D}}^{*}{)}^{0}{\ensuremath{\pi}}^{0}$ using ${e}^{+}{e}^{\ensuremath{-}}$ collision data samples with integrated luminosities of $1092\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ at $\sqrt{s}=4.23\text{ }\text{ }\mathrm{GeV}$ and $826\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ at $\sqrt{s}=4.26\text{ }\text{ }\mathrm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $({D}^{*}{\overline{D}}^{*}{)}^{0}$ mass threshold in the ${\ensuremath{\pi}}^{0}$ recoil mass spectrum, which we denote as ${Z}_{c}(4025{)}^{0}$. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be $(4025.{5}_{\ensuremath{-}4.7}^{+2.0}\ifmmode\pm\else\textpm\fi{}3.1)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $(23.0\ifmmode\pm\else\textpm\fi{}6.0\ifmmode\pm\else\textpm\fi{}1.0)\text{ }\text{ }\mathrm{MeV}$, respectively. The Born cross sections of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{Z}_{c}(4025{)}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}({D}^{*}{\overline{D}}^{*}{)}^{0}{\ensuremath{\pi}}^{0}$ are measured to be $(61.6\ifmmode\pm\else\textpm\fi{}8.2\ifmmode\pm\else\textpm\fi{}9.0)\text{ }\text{ }\mathrm{pb}$ at $\sqrt{s}=4.23\text{ }\text{ }\mathrm{GeV}$ and $(43.4\ifmmode\pm\else\textpm\fi{}8.0\ifmmode\pm\else\textpm\fi{}5.4)\text{ }\text{ }\mathrm{pb}$ at $\sqrt{s}=4.26\text{ }\text{ }\mathrm{GeV}$. The first uncertainties are statistical and the second are systematic.

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