Weakly bound states with spin-isospin symmetry

International audienceWe discuss weakly bound states of a few-fermion system having spin-isospin symmetry. This corresponds to the nuclear physics case in which the singlet, a_0, and triplet, a_1, n - p scattering lengths are large with respect to the range of the nuclear interaction. The ratio of the two is about a_0/a_1 sim -4.31. This value defines a plane in which a_0 and a_1 can be varied up to the unitary limit, 1/a_0 = 0 and 1/a_1 = 0, maintaining its ratio fixed. Using a spin dependant potential model we estimate the three-nucleon binding energy along that plane. This analysis can be considered an extension of the Efimov plot for three bosons to the case of three 1/2-spin-isospin fermions