Electric dipole polarizability of $^{40}$Ca

TL;DR

This study measures the electric dipole polarizability of $^{40}$Ca using proton scattering and photoabsorption data, providing critical tests for theoretical nuclear models and insights into neutron skin and nuclear matter properties.

Contribution

It offers the first precise measurement of $^{40}$Ca's electric dipole polarizability and compares it with advanced theoretical calculations, enhancing understanding of nuclear structure.

Findings

Measured $ ext{α}_ ext{D}$ for $^{40}$Ca as 1.92(17) fm$^3$

Theoretical models accurately describe dipole polarizabilities in medium-mass nuclei

Results constrain neutron skin thickness and nuclear equation of state

Abstract

The electric dipole strength distribution in $^{40}$Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at very forward angles. Combined with total photoabsorption data at higher excitation energy, this enables an extraction of the electric dipole polarizability $\alpha_\mathrm{D}$($^{40}$Ca) = 1.92(17) fm$^3$. Together with the measured $\alpha_{\rm D}$ in $^{48}$Ca, it provides a stringent test of modern theoretical approaches, including coupled cluster calculations with chiral effective field theory interactions and state-of-the art energy density functionals. The emerging picture is that for this medium-mass region dipole polarizabilities are well described theoretically, with important constraints for the neutron skin in $^{48}$Ca and related equation of state quantities.