Spectroscopy of the neutron-rich hypernucleus \(^{7}_{\Lambda}\)He from electron scattering

The missing mass spectroscopy of the \(^{7}_{\Lambda}\)He hypernucleus was performed, using the \(^{7}\)Li\((e,e^{\prime}K^{+})^{7}_{\Lambda}\)He reaction at the Thomas Jefferson National Accelerator Facility Hall C. The \(\Lambda\) binding energy of the ground state (1/2\(^{+}\)) was determined with a smaller error than that of the previous measurement, being \(B_{\Lambda}\) = 5.55 \(\pm\) 0.10(stat.) \(\pm\) 0.11(sys.) MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at \(B_{\Lambda}\) = 3.65 \(\pm\) 0.20(stat.) \(\pm\) 0.11(sys.) MeV was observed and assigned as a mixture of 3/2\(^{+}\) and 5/2\(^{+}\) states, confirming the "gluelike" behavior of \(\Lambda\), which makes an unstable state in \(^{6}\)He stable against neutron emission.