From 2011 to 2014, the BESIII experiment collected about 5 fb$^{ -1}$ data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states. By analyzing the di-muon process $e^{ +}e^{ -}\rightarrow\gamma_{ \rm ISR/FSR}\mu^{ +}\mu^{ -}$, the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV. The center-of-mass energy is found to be stable for most of time during the data taking.
Categories: hep-ex