Precision Measurement of the e+e-→Λc+Λ¯c- Cross Section Near Threshold

The cross section of the e ⁺e ^- → $\text{Î}{\text{›}}_c^{+}$$\overline{\text{Î}\text{›}}$${}_c^{-}$ process is measured with unprecedented precision using data collected with the BESIII detector at √s = 4574.5, 4580.0, 4590.0 and 4599.5 MeV. The non-zero cross section near the $\text{Î}{\text{›}}_c^{+}$$\overline{\text{Î}\text{›}}$${}_c^{-}$ production threshold is cleared. At center-of-mass energies √s = 4574.5 and 4599.5 MeV, the higher statistics data enable us to measure the Λ_c polar angle distributions. From these, the Λ_c electric over magnetic form factor ratios (|GE/GM|) are measured for the first time. They are found to be 1.14±0.14±0.07 and 1.23±0.05±0.03 respectively, where the first uncertainties are statistical and the second are systematic.