Observation of a neutral charmoniumlike state $Z_c(4025{)}^0$ in $e^{+}{e}^{-}\to (D^{\ast }{\bar{D}}^{\ast }{)}^0{\pi }^0$

We report a study of the process $e^{+} e^{-} \to (D^{} \bar{D}^{})^{0} \pi^0$using$e^+e^-$collisiondatasampleswithintegratedluminositiesof$1092 \rm{pb}^{-1}$at$\sqrt{s}=4.23 \rm{GeV}$and$826 \rm{pb}^{-1}$at$\sqrt{s}=4.26 \rm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $(D^{} \bar{D}^{})^{0}$massthresholdinthe$\pi^0$ 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 $(4025.5_{-4.7}^{+2.0}\pm 3.1)\mathrm{M}\mathrm{e}\mathrm{V}\mathrm{/}{c}^2$ and $(23.0\pm 6.0\pm 1.0)\mathrm{M}\mathrm{e}\mathrm{V}$, respectively. The Born cross sections of $e^{+}{e}^{-}\to Z_c(4025{)}^0{\pi }^0\to (D^{\ast }{\bar{D}}^{\ast }{)}^0{\pi }^0$ are measured to be $(61.6\pm 8.2\pm 9.0)\mathrm{p}\mathrm{b}$ at $\sqrt{s}=4.23\mathrm{G}\mathrm{e}\mathrm{V}$ and $(43.4\pm 8.0\pm 5.4)\mathrm{p}\mathrm{b}$ at $\sqrt{s}=4.26\mathrm{G}\mathrm{e}\mathrm{V}$. The first uncertainties are statistical and the second are systematic.