Observation of
M. Ablikim (Institute of High Energy Physics, China); M. N. Achasov (Also at the Novosibirsk State University, Novosibirsk, Russia, G.I. Budker Institute of Nuclear Physics SB RAS (BINP), Russia); P. Adlarson (Uppsala University, Box 516, Sweden); M. Albrecht (Bochum Ruhr-University, Germany); R. Aliberti (Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, Germany); et al - Show all 572 authors
Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 $ \rm fb^{-1} $ , the process $ \rm fb^{-1} $ is observed for the first time with a statistical significance of $ \rm fb^{-1} $ . The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be $ \rm fb^{-1} $ fb, $ \rm fb^{-1} $ fb and $ \rm fb^{-1} $ fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the $ \rm fb^{-1} $ and $ \rm fb^{-1} $ invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.