Accurate nuclear radii and binding energies from a chiral interaction

Abstract

With the goal of developing predictive ab-initio capability for light and medium-mass nuclei, twonucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLOsat, yield accurate binding energies and radii of nuclei up to 40 Ca, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective J π = 3 − states in 16 O and 40 Ca are described accurately, while spectra for selected p-and sd-shell nuclei are in reasonable agreement with experiment. Introduction -Interactions from chiral effective field theory (EFT) [1][2][3][4] and modern applications of renormalization group techniques [5][6][7][8] have opened the door for a description of atomic nuclei consistent with the underlying symmetries of quantum chromodynamics, the theory of the strong interaction. Chiral nuclear forces can be constructed systematically from long-range pion physics augmented by contact interactions. Over the past decade, the renaissance of nuclear theory based on realistic nuclear forces and powerful computational methods has pushed the frontier of ab initio calculations from fewbody systems and light nuclei [6, 9, 10] to medium-mass nuclei [11][12][13][14][15][16][17][18][19].

Chiral three-nucleon forces and the evolution of correlations along the oxygen isotopic chain

“…We observe that all these deficiencies might be corrected by having extra short-range repulsion in the NN section of the Hamiltonian. Other approaches, such as global fittings of chiral NN+3N forces to include medium mass isotopes, also hold the promise to reach proper saturation [76]. In general, it is found that the current NN-N3LO interaction with cutoff at 500 MeV, augmented by the local 3NF-NNLO with a 400 MeV local cutoff, tends to stretch the single particle spectrum too much compared to data.…”

In-medium similarity renormalization group for closed and open-shell nuclei

“…In section 6, we will present MR-IMSRG results with one of the first new N N +3N interactions that resulted from these efforts, NNLO sat [26]. By taking select many-body data into account in the optimization procedure, the creators of NNLO sat were able to improve the interaction's saturation properties, allowing an accurate description of the ground-state energies and radii of 40,48 Ca [140,141].…”

“…One of the first new interactions to come out of these efforts is NNLO sat by Ekström and collaborators [26]. As the name suggests, it is defined at chiral order NNLO, and contains N N and 3N interactions.…”

“…The many-body data, e.g., selected radii, are chosen in order to improve the deficient saturation behavior of chiral interactions that are used as input for nuclear many-body calculations. The first interaction optimized with this protocol is NNLO sat [26], which is able to accurately describe the ground-state energies and charge radii of 40,48 Ca at the same time. Following the same philosophy but not the same approach, Shirokov et al have produced Daejeon16, a softened chiral N N interaction that has been tuned for the description of light nuclei without explicit 3N forces [27][28][29][30].…”

Asymmetric nuclear matter based on chiral two- and three-nucleon interactions

“…For symmetric matter it was found that low-momentum NN plus 3N interactions are capable to predict realistic saturation properties, with 3N forces fit only to few-body data [7], whereas neutron matter was found to be perturbative [8]. In subsequent studies, symmetric matter and neutron matter were also investigated based on chiral EFT interactions within the self-consistent Green's function framework [9,10], using coupled-cluster theory [11,12], with in-medium chiral perturbation theory [13] and in many-body perturbation theory [14]. Furthermore, the development of novel local chiral NN forces opened the way to first Quantum Monte Carlo studies of neutron matter based on chiral EFT interactions [15][16][17][18].…”