Observation of a Neutral Structure near the $D{\bar{D}}^{\ast }$ Mass Threshold in $e^{+}{e}^{-}\to (D{\bar{D}}^{\ast }{)}^0{\pi }^0$ at $\sqrt{s}$ = 4.226 and 4.257 GeV

A neutral structure in the $D{\bar{D}}^{\ast }$ system around the $D{\bar{D}}^{\ast }$ mass threshold is observed with a statistical significance greater than 10$\sigma$ in the processes $e^{+}{e}^{-}\to D^{+}{D}^{\ast -}{\pi }^0+c\mathrm{.}c\mathrm{.}$ and $e^{+}{e}^{-}\to D^0{\bar{D}}^{\ast 0}{\pi }^0+c\mathrm{.}c\mathrm{.}$ at $\sqrt{s}$ = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as $Z_c(3885{)}^0$. Assuming the presence of a resonance, its pole mass and width are determined to be ($3885.7_{-5.7}^{+4.3}$(stat)$\pm 8.4$(syst)) MeV/$c^2$ and ($35_{-12}^{+11}$(stat)$\pm 15$(syst)) MeV, respectively. The Born cross sections are measured to be $\sigma(e^{+}e^{-}\to Z_{c}(3885)^{0}\pi^{0}, Z_{c}(3885)^{0} \to D\bar{D}^{})=(77 \pm 13$(stat)$\pm 17$(syst))pbat4.226GeVand($47 \pm 9$(stat)$ \pm 10$(syst)) pb at 4.257 GeV. The ratio of decay rates $\frac{$\mathcal{B}$({Z_{c}(3885)^{0} \to D^{+}D^{-}+c.c.})}{$\mathcal{B}$({Z_{c}(3885)^{0} \to D^{0}\bar{D}^{*0}+c.c.})}$isdeterminedtobe$0.96 \pm 0.18$(stat)$\pm 0.12$(syst), consistent with no isospin violation in the process $Z_c(3885{)}^0\to D{\bar{D}}^{\ast }$.