Observation of a neutral charmoniumlike state $Z_c(4025)^0$ in $e^+ e^- \to (D^* \barD^*)^0 \pi^0$

摘要: We report a study of the process e+e−→(D∗D¯∗)0π0 using e+e− collision data samples with integrated luminosities of 1092pb−1 at s√=4.23GeV and 826pb−1 at s√=4.26GeV 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√=4.23GeV and (43.4±8.0±5.4)pb at s√=4.26GeV. The first uncertainties are statistical and the second are systematic.