We compute the charge radii and ground-state energies of even-mass neon and magnesium isotopes from neutron number N=8 to the dripline. Our calculations are based on nucleon-nucleon and three-nucleon ...potentials from chiral effective field theory that include Δ isobars. These potentials yield an accurate saturation point and symmetry energy of nuclear matter. We use the coupled-cluster method and start from an axially symmetric reference state. Binding energies and two-neutron separation energies largely agree with data, and the dripline in neon is accurate. The computed charge radii are accurate for many isotopes where data exist. Finer details, such as isotope shifts, however, are not accurately reproduced. These chiral potentials indicate a subshell closure at N=14 for the radii (but not for two-neutron separation energies) and a decrease in charge radii at N=8 (observed in neon and predicted for magnesium). They yield a continued increase of charge radii as neutrons are added beyond N=14 yet underestimate the large increase at N=20 in magnesium.
The neutron skin of atomic nuclei impacts the structure of neutron-rich nuclei, the equation of state of nucleonic matter, and the size of neutron stars. Here we predict the neutron skin of selected ...light- and medium-mass nuclei using coupled-cluster theory and the auxiliary field diffusion Monte Carlo method with two- and three-nucleon forces from chiral effective field theory. We find a linear correlation between the neutron skin and the isospin asymmetry in agreement with the liquid-drop model and compare with data. We also extract the linear relationship that describes the difference between neutron and proton radii of mirror nuclei and quantify the effect of charge symmetry breaking terms in the nuclear Hamiltonian. Our results for the mirror-difference charge radii and binding energies per nucleon agree with existing data.
Abstract
Nuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for ...nuclear theory. Experimental evidence suggested a new magic neutron number at
N
= 32 (refs.
1–3
) in the calcium region, whereas the unexpectedly large increases in the charge radii
4,5
open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with β-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond
N
= 32. Here we provide a charge radius measurement of
52
K. It does not show a signature of magic behaviour at
N
= 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd–even variations in charge radii but not the notable increase beyond
N
= 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd–even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory.
Two-Neutron Halo is Unveiled in F 29 Bagchi, S.; Kanungo, R.; Tanaka, Y. K. ...
Physical review letters,
06/2020, Letnik:
124, Številka:
22
Journal Article
Recenzirano
Odprti dostop
We report the measurement of reaction cross sections (σexR) of 27,29F with a carbon target at RIKEN. The unexpectedly large σexR and derived matter radius identify 29F as the heaviest two-neutron ...Borromean halo to date. The halo is attributed to neutrons occupying the 2p3/2 orbital, thereby vanishing the shell closure associated with the neutron number N=20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of 27F but are challenged for 29F.
We use coupled-cluster theory and nuclear interactions from chiral effective field theory to compute the nuclear matrix element for the neutrinoless double-$\beta$ decay of $^{48}$Ca. Benchmarks with ...the no-core shell model in several light nuclei inform us about the accuracy of our approach. For $^{48}$Ca we find a relatively small matrix element. We also compute the nuclear matrix element for the two-neutrino double-$\beta$ decay of $^{48}$Ca with a quenching factor deduced from two-body currents in recent ab initio calculation of the Ikeda sum rule in $^{48}$Ca Gysbers et al., Nat. Phys. 15, 428 (2019).
We calculate the magnetic moments of light nuclei $( A < 20 )$ using the auxiliary field diffusion Monte Carlo method and local two- and three-nucleon forces with electromagnetic currents from chiral ...effective field theory. For all nuclei under consideration, we also calculate the ground-state energies and charge radii. We generally find a good agreement with experimental values for all of these observables. For the electromagnetic currents, we explore the impact of employing two different power counting schemes, and study theoretical uncertainties stemming from the truncation of the chiral expansion order by order for select nuclei within these two approaches. In conclusion, we find that it is crucial to employ consistent power counting schemes for interactions and currents to achieve a systematic order-by-order convergence.
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