Using a data sample corresponding to an integrated luminosity of 11.3 collected at center-of-mass energies from to ~GeV with the BESIII detector, we observe the process for the first time with a statistical significance of . The ratio of average cross sections for over is determined to be , which is consistent with expectations from isospin symmetry. Here and below, the first uncertainties are statistical and the second are systematic. The mass of the is measured to be ~MeV/. Due to the limited statistics, the intrinsic width of the is measured as an upper limit of ~MeV at confidence level.

生成讲解博客的中文版本

生成AI智能校验的中文版本