Microscopic Optical Potentials from First Principles

We construct nucleonic microscopic optical potentials by combining the Green’s function approach with the coupled-cluster method for \(^{40}\mathrm {Ca}\) and \(^{48}\mathrm {Ca}\). We work with the chiral nucleon-nucleon and three-nucleon interaction \(\mathrm {NNLO_{sat}}\) which reproduces the charge radii of \(^{40}\)Ca and \(^{48}\)Ca. The overall form of the neutron scattering cross section is reproduced for both nuclei, but the imaginary part of the calculated potential, which reflects the loss of flux in the elastic channel, is negligible. The latter points to many-body correlations that would appear beyond the coupled-cluster truncation level considered in this work. We show that, by artificially increasing the parameter \(\eta \) in the Green’s function, practical results can be further improved.