Role of three-nucleon forces and many-body processes in nuclear pairing

Abstract

We present microscopic valence-shell calculations of pairing gaps in the calcium isotopes, focusing on the role of three-nucleon (3N) forces and many-body processes. In most cases, we find a reduction in pairing strength when the leading chiral 3N forces are included, compared to results with low-momentum two-nucleon (NN) interactions only. This is in agreement with a recent energy density functional study. At the NN level, calculations that include particle-particle and hole-hole ladder contributions lead to smaller pairing gaps compared with experiment. When particle-hole contributions as well as the normal-ordered one- and two-body parts of 3N forces are consistently included to third order, we find reasonable agreement with experimental three-point mass differences. This highlights the important role of 3N forces and many-body processes for pairing in nuclei. Finally, we relate pairing gaps to the evolution of nuclear structure in neutron-rich calcium isotopes and study the predictions for the 2+ excitation energies, in particular for 54Ca.

8 pages, 5 figures, minor changes, published version

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• Nonperturbative shell-model interactions from the in-medium similarity renormalization group
• Nuclear forces and their impact on neutron-rich nuclei and neutron-rich matter
• Ab-initio coupled-cluster effective interactions for the shell model: Application to neutron-rich oxygen and carbon isotopes
• Measurement and microscopic description of odd-even staggering of charge radii of exotic copper isotopes
• Exploring sd-shell nuclei from two- and three-nucleon interactions with realistic saturation properties
• Three-nucleon forces and spectroscopy of neutron-rich calcium isotopes
• Quantum Monte Carlo calculations of neutron matter with non-local chiral interactions
• New applications of renormalization group methods in nuclear physics
• Realistic shell-model calculations for isotopic chains "north-east'' of 48Ca in the (N,Z) plane
• New determination of double-beta-decay properties in 48Ca: high-precision Q-value measurement and improved nuclear matrix element calculations
• Symmetry energy, neutron skin, and neutron star radius from chiral effective field theory interactions
• Structure of 55Sc and development of the N=34 subshell closure
• The Nuclear Pairing Gap -- How Low Can It Go?
• Global phenomenological descriptions of nuclear odd-even mass staggering
• $\mathbf{N}=32$ shell closure below calcium: Low-lying structure of ${}^{50}$Ar
• Effects of the tensor force on the ground and first $2^{+}$ states of the magic ${}^{54}$Ca nucleus
• Uncovering the mechanism of chiral three-nucleon force in driving spin-orbit splitting
• Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes
• Detailed spectroscopy of ${}^{46}$Ca: A study of the ${\beta }^{-}$ decay of ${}^{46}$K
• Neutrinoless Double-Beta Decay and Realistic Shell Model
• The calculation of single-nucleon energies of nuclei by considering two-body effective interaction, n(k,rho), and a Hartree-Fock inspired scheme