Electric dipole polarizability of Ca 40 [Electric dipole polarizability of ⁴⁰Ca]

The electric dipole strength distribution in Ca40 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 αD(40Ca)=1.92(17) fm3. Together with the measured αD in Ca48, 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 Ca48 and related equation of state quantities.