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

Abstract

Background: Three-nucleon forces (3NFs) have non trivial implications on the evolution of correlations at extreme proton-neutron asymmetries. Recent ab initio calculations show that leading order chiral interactions are crucial to obtain the correct binding energies and neutron driplines along the O, N, and F chains, Ref.[A. Cipollone, C. Barbieri, P. Navrátil, Phys. Rev. Lett 111, 062501 (2013)].Purpose: Here, we discuss the impact of 3NFs along the oxygen chain for other quantities of interest, such has the spectral distribution for attachment and removal of a nucleon, spectroscopic factors and radii. The objective is to better delineate the general effects of 3NFs on nuclear correlations. Methods:We employ self-consistent Green's function (SCGF) theory which allows a comprehensive calculation of the single particle spectral function. For the closed subshell isotopes, 14 O, 16 O, 22 O, 24 O and 28 O, we perform calculations with the Dyson-ADC(3) method which is fully non-perturbative and is the state of the art for both nuclear physic and quantum chemistry applications. The remaining open shell isotopes are studied using the newly developed Gorkov-SCGF formalism up to second order. Results:We produce complete plots for the spectral distributions. The spectroscopic factors for the dominant quasiparticle peaks are found to depend very little on the leading order (NNLO) chiral 3NFs. The latters have small impact on the calculated matter radii, which, however are consistently obtained smaller than experiment. Similarly, single particle spectra tend to be too spread with respect to the experiment. This effect might hinder, to some extent, the onset of correlations and screen the quenching of calculated spectroscopic factors. The most important effect of 3NFs is thus the fine tuning of the energies for the dominant quasiparticle states, which governs the shell evolution and the position of driplines.Conclusions: Although present chiral NNLO 3NFs interactions do reproduce the binding energies correctly in this mass region, the details of the nuclear spectral function remain at odd with the experiment showing too small radii and a too spread single particle spectrum, similar to what already pointed out for larger masses. This suggests a lack of repulsion in the present model of NN+3N interactions which is mildly apparent already for masses in the A=14-28 range.

Differential cross section measurement of the 12C(e,e’pp)10Beg.s. reaction

“…The importance of nuclear correlations was established, for example, in the early (e,e p) experiments [6][7][8] from which strong reductions of single particle strength was inferred. While such measurements might have initially been conjectured to be short-range effects, later calculations clearly demonstrated that they must be ascribed almost completely to LRC dynamics [2,9,10]. This is confirmed by (e,e p) observations at small missing energies and large missing momenta [11,12].…”

“…In the present paper we report the results of a measurement of the 12 C(e,e pp) 10 Be reaction performed at MAMI in super-parallel kinematics, that is sensitive to the one-body emission channel, and partially suppresses other mechanisms capable to produce two protons in the final state. A silicon detector telescope (SDT) for proton detection has been developed [35] and employed along with two high-resolution magnetic spectrometers of the A1 Collaboration [36] that have been used for detecting the scattered electron and the other proton.…”

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

“…[55,62]. Note that the ADC(3) Self-Consistent Green's Function results [128,159] were obtained for λ = 2.0 fm −1 , but the dependence of energies on λ is very weak. Black bars indicate experimental data [110].…”

“…In addition to IT-NCSM, CCSD, and Λ-CCSD(T) (cf. 5.4), we also include results from the Self-Consistent Green's Function (SCGF) approach in the ADC(3) scheme [128,159]. The latter are obtained at a slightly different resolution scale λ = 2.0 fm −1 , but the dependence of the ground-state energies on λ is very weak, at least in the range λ = 1.88, .…”

“…The oxygen isotopic chain has become a testing ground for ab initio nuclear structure methods in recent years [55,91,128,[159][160][161][162][163][164][165], mainly for two reasons: First, Otsuka et al [160] showed the impact of 3N forces on the location of the neutron drip line, and second, exact results from the importance-truncated NCSM (IT-NCSM) [56,91,166,167] are available for the ground states and low-lying excitations, allowing us to assess the many-body uncertainties of our calculations.…”