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

We report a study of the process e⁺e⁻ → (DD̅)⁰ π⁰ using e⁺e⁻ collision data samples with integrated luminosities of 1092 pb⁻¹ at √s̅ = 4.23 GeV and 826 pb⁻¹ at √s̅ = 4.26 GeV collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the (DD̅)⁰ mass threshold in the π⁰ 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) ± 3.1) MeV/c² and (23.0 ± 6.0 ± 1.0) MeV, respectively. The Born cross sections of e⁺e⁻→ Z_c(4025)⁰π⁰ → (DD̅)⁰ π⁰ are measured to be (61.6 ± 8.2 ± 9.0) pb at √s̅ = 4.23 GeV and (43.4 ± 8.0 ± 5.4) pb at √s̅ = 4.26 GeV. The first uncertainties are statistical and the second are systematic.