Spin-dipole strength functions of $^4$He with realistic nuclear forces

TL;DR

This study investigates the spin-dipole excitations of helium-4 using realistic nuclear forces and complex scaling, achieving good agreement with observed resonance energies and widths, and exploring sum rules related to tensor correlations.

Contribution

It presents a detailed theoretical analysis of spin-dipole strength functions in helium-4 with realistic forces, including continuum states and decay channels, using the complex scaling method.

Findings

Resonance energies and widths match experimental data.

Spin-dipole sum rules relate to tensor correlations.

Explicit treatment of decay channels improves accuracy.

Abstract

Both isoscalar and isovector spin-dipole excitations of $^4$He are studied using realistic nuclear forces in the complex scaling method. The ground state of $^4$He and discretized continuum states with $J^{\pi}=0^-, 1^-, 2^-$ for A=4 nuclei are described in explicitly correlated Gaussians reinforced with global vectors for angular motion. Two- and three-body decay channels are specifically treated to take into account final state interactions. The observed resonance energies and widths of the negative-parity levels are all in fair agreement with those calculated from both the spin-dipole and electric-dipole strength functions as well as the energy eigenvalues of the complex scaled Hamiltonian. Spin-dipole sum rules, both non energy-weighted and energy-weighted, are discussed in relation to tensor correlations in the ground state of $^4$He.