Giant and pigmy dipole resonances in 4He, 16,22O, and 40Ca from chiral nucleon-nucleon interactions

TL;DR

This paper advances the computational methods for studying inelastic nuclear reactions, applying them to calculate giant dipole resonances in various nuclei using chiral nucleon interactions, and compares results with experimental data.

Contribution

It introduces a reformulation of the Lorentz integral transform method within coupled-cluster theory for inelastic reactions, enabling calculations of giant dipole resonances in nuclei.

Findings

Successfully computed giant dipole resonances in 4He, 16O, 22O, and 40Ca.

Found a low-lying E1 strength in neutron-rich 22O consistent with experimental data.

Identified deficiencies in the Hamiltonian leading to overbinding and underestimated polarizability in 40Ca.

Abstract

We combine the coupled-cluster method and the Lorentz integral transform for the computation of inelastic reactions into the continuum. We show that the bound-state-like equation characterizing the Lorentz integral transform method can be reformulated based on extensions of the coupled-cluster equation-of-motion method, and we discuss strategies for viable numerical solutions. Starting from a chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order, we compute the giant dipole resonances of 4He, 16,22O and 40Ca, truncating the coupled-cluster equation-of-motion method at the two-particle-two-hole excitation level. Within this scheme, we find a low-lying E1 strength in the neutron-rich 22O nucleus, which compares fairly well with data from [Leistenschneider et al. Phys. Rev. Lett. 86, 5442 (2001)]. We also compute the electric dipole polariziability in 40Ca. Deficiencies of the employed Hamiltonian lead to overbinding, too small charge radii and a too small electric dipole polarizability in 40Ca.