title: He 4 4He + n + n continuum within an ab initio framework.
abstract: The low-lying continuum spectrum of the (6)He nucleus is investigated for the first time within an ab initio framework that encompasses the (4)He + n + n three-cluster dynamics characterizing its lowest decay channel. This is achieved through an extension of the no-core shell model combined with the resonating-group method, in which energy-independent nonlocal interactions among three nuclear fragments can be calculated microscopically, starting from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with three-body scattering boundary conditions by means of the hyperspherical-harmonics method on a Lagrange mesh. Using a soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we find the known J(π) = 2(+) resonance as well as a result consistent with a new low-lying second 2(+) resonance recently observed at GANIL at 2.6 MeV above the (6)He ground state. We also find resonances in the 2(-), 1(+), and 0(-) channels, while no low-lying resonances are present in the 0(+) and 1(-) channels.
authors.affiliation: TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada.
authors.forename: Carolina
authors.initials: C
authors.lastname: Romero-Redondo
authors.affiliation: Lawrence Livermore National Laboratory, P.O. Box 808, L-414, Livermore, California 94551, USA.
authors.forename: Sofia
authors.initials: S
authors.lastname: Quaglioni
authors.affiliation: TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada.
authors.forename: Petr
authors.initials: P
authors.lastname: Navrátil
authors.affiliation: Lawrence Livermore National Laboratory, P.O. Box 808, L-414, Livermore, California 94551, USA.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Hupin