Structure of the6Li→p+(nα) vertex:Li6(e,e’p)nαreaction

Three-body models of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ are used to describe the reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(e,e’p)nα. Under the impulse approximation, the differential cross section for the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$(e,e’p)nα reaction with unpolarized particles factorizes into a product of a kinematical factor, the (off-shell) electron-proton cross section, and a distorted spectral function of the ejected proton in the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ nucleus. A prescription by De Forest is used to carry the ep cross section off the proton mass shell. The spectral function, containing all of the nuclear physics in the reaction, is found from the ${}_{}{}^6{}_{}{}^{}$Li→p+(nα) vertex amplitude. A unified theoretical description of both the bound state and the (nα) scattering state is employed to predict the ${}_{}{}^6{}_{}{}^{}$Li→p+(nα) vertex amplitude. For (nα) relative energies below 16 MeV and proton momenta below 200 MeV/c, the $P_{3/2}$ αN resonance dominates the shape of the spectral function. However, the contribution of the outgoing scattering wave due to the $S_{1/2}$ αN interaction has a significant role for momenta of the (nα) pair below 40 MeV/c, making the 2s orbitals in ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ control the behavior of the momentum distribution near zero momentum transfer to the (nα) pair. Recent coincidence experiments give good agreement with theory. Experimental resolutions are currently not quite capable of discriminating between various $S_{1/2}$ αN interactions used in the three-body calculation.