Sensitivity of neutron radii in a²⁰⁸Pb nucleus and a neutron star to nucleon-σ-ρ coupling corrections in relativistic mean field theory

We study the sensitivity of the neutron skin thickness S in a ²⁰⁸Pb nucleus to the addition of nucleon-σ-ρ coupling corrections to a selection (PK1, NL3, S271, and Z271) of interactions in a relativistic mean field model. The PK1 and NL3 effective interactions lead to a minimum value of S = 0.16 fm in comparison with the original value of S = 0.28 fm. The S271 and Z271 effective interactions yield even smaller values of S = 0.11 fm, which are similar to those for nonrelativistic mean field models. A precise measurement of the neutron radius, and therefore S, in ²⁰⁸Pb will place an important constraint on both relativistic and nonrelativistic mean field models. We also study the correlation between the radius of a 1.4-solar-mass neutron star and S.