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

We report a study of the process e+e−→(D∗D¯∗)0π0 using e+e− collision data samples with integrated luminosities of 1092  pb−1 at s√=4.23  GeV and 826  pb−1 at s√=4.26  GeV collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the (D∗D¯∗)0 mass threshold in the π0 recoil mass spectrum, which we denote as Zc(4025)0. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be (4025.5+2.0−4.7±3.1)  MeV/c2 and (23.0±6.0±1.0)  MeV, respectively. The Born cross sections of e+e−→Zc(4025)0π0→(D∗D¯∗)0π0 are measured to be (61.6±8.2±9.0)  pb at s√=4.23  GeV and (43.4±8.0±5.4)  pb at s√=4.26  GeV. The first uncertainties are statistical and the second are systematic.