Study of the nnΛ State and Λn Interaction at Jefferson Lab

An n n Λ , which consists of two neutrons and a Lambda hyperon, is a multi-baryon system with no charge. Studying the n n Λ state would provide information about the Λ n interaction which has not been directly measured by a scattering experiment. The experiment (E12-17-003) was performed in order to search for the n n Λ state at Jefferson Lab. The n n Λ is expected to be produced by the ( e , e ′ K + ) reaction, which has sensitivity to both bound and resonance states if the natural width of the n n Λ is narrow enough to be observed as a peak. The experiment used gas targets of hydrogen and tritium for mass calibration and the n n Λ production, respectively. The mass calibration with H ( e , e ′ K + ) Λ / Σ 0 reactions gave the mass resolution of the Λ and Σ 0 each 3.5 MeV / c 2 FWHM, for the elementary reaction. A spectrum of 3 H ( e , e ′ K + ) X was obtained, and a simple model with a Λ n final state interaction was applied to reproduce the spectrum.