Resonances in the Λnn system

Background: A bound state of the Lambda nn system has been reported, but at least three theoretical papers question the existence of such a bound state. Purpose: We address the alternative question of whether there might exist a resonance in the Lambda nn system, using a rank-one separable potential formulation of the Hamiltonian. Methods: We examine the eigenvalues of the kernel of the Faddeev equation in the complex energy plane using contour rotation to allow us to analytically continue the kernel onto the second energy sheet. The model Lambda n interaction is fitted to the Lambda p scattering length and effective range. Results: We follow the largest eigenvalue as the Lambda n potentials are scaled and the Lambda nn continuum is turned first into a resonance, and then into a bound state of the system. Conclusions: Because a change in the strength of the Lambda n potential of as little as 5% will produce a Lambda nn resonance, we infer that an experiment of the H-3(e, e'K+)(Lambda)(3)n type at JLAB could be used to constrain the properties of the Lambda n interaction.