Two methods for the determination of beam energy spread near Λ c + Λ̄ c − production threshold

Two techniques are introduced to measure the beam energy spread in collision experiments of high energy physics, based on the threshold truncation effect and the beam-constrained mass spectra resolution, respectively. Both techniques are verified by Monte Carlo simulation, and take advantage of the BESIII collected data near the Λc+Λ̄c− production threshold. The measured results are consistent with each other, and also accord with the extrapolation from the value measured at the J/ψ resonance.