High resolution spectroscopic study of Be Λ10

Spectroscopy of a BeΛ10 hypernucleus was carried out at JLab Hall C using the (e,e′K+) reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of ∼0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using p(e,e′K+)Λ,Σ0 reactions allowed us to determine the energy levels; and the binding energy of the ground-state peak (mixture of 1- and 2- states) was found to be BΛ=8.55±0.07(stat.)±0.11(sys.) MeV. The result indicates that the ground-state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on the charge symmetry breaking effect in the ΛN interaction.