[2] Since 2003 a frontier for the Standard Model (SM) has emerged at low energies through XYZ particle discoveries.
The well-established theory of Quantum Chromodynamics (QCD) is tested by many exotic charmonium discoveries since the X(3872) was first identified at the Belle experiment in 2003.
More than two dozen previously unpredicted charmonium- and bottomonium-like states have been discovered, and the understanding of heavy quarkonium physics is undetermined.
[5][6] While each of these three types of states have had some success of explaining the newly discovered particle, a complete explanation has not been found.
The BES III collaboration in 2012 started taking data at 4260 MeV and could observe direct production instead of B decay or Initial State Radiation to continue the study with a higher luminosity.