Background: The nuclear optical potential is a successful tool for the study of nucleon-nucleus elastic scattering and its use has been further extended to inelastic scattering and other nuclear reactions. The nuclear density of the target nucleus is a fundamental ingredient in the construction of the optical potential and thus plays an important role in the description of the scattering process. Purpose: In this work we derive a microscopic optical potential for intermediate energies using ab initio translationally invariant nonlocal one-body nuclear densities computed within the no-core shell model (NCSM) approach utilizing two-and three-nucleon chiral interactions as the only input. Methods: The optical potential is derived at first-order within the spectator expansion of the nonrelativistic multiple scattering theory by adopting the impulse approximation. Nonlocal nuclear densities are derived from the NCSM one-body densities calculated in the second quantization. The translational invariance is generated by exactly removing the spurious center-of-mass (COM) component from the NCSM eigenstates. Results: The ground state local and nonlocal densities of 4,6,8 He, 12 C, and 16 O are calculated and applied to optical potential construction. The differential cross sections and the analyzing powers for the elastic proton scattering off these nuclei are then calculated for different values of the incident proton energy. The impact of nonlocality and the COM removal is discussed. Conclusions: The use of nonlocal densities has a substantial impact on the differential cross sections and improves agreement with experiment in comparison to results generated with the local densities especially for light nuclei. For the halo nuclei 6 He and 8 He, the results for the differential cross section are in a reasonable agreement with the data although a more sophisticated model for the optical potential is required to properly describe the analyzing powers.

Background: In a previous series of papers we investigated the domain of applicability of chiral potentials to the construction of a microscopic optical potential (OP) for elastic nucleon-nucleus scattering. The OP was derived at the first order of the spectator expansion of the Watson multiple scattering theory and its final expression was a folding integral between the nucleon-nucleon (NN) t matrix and the nuclear density of the target. In the calculations NN and three-nucleon (3N) chiral interactions were used for the target density and only the NN interaction for the NN t matrix. Purpose: The purpose of this work is to achieve another step towards the calculation of a more consistent OP introducing the 3N force also in the dynamic part of the OP. Methods: The full treatment of the 3N interaction is beyond our present capabilities. Thus, in the present work it is approximated with a density dependent NN interaction obtained after the averaging over the Fermi sphere. In practice, in our model the 3N force acts as a medium correction of the bare NN interaction used to calculate the t matrix. Even if the 3N force is treated in an approximate way, this method naturally extends our previous model of the OP and allows a direct comparison of our present and previous results. Results: We consider as case studies the elastic scattering of nucleons off 12 C and 16 O. We present results for the differential cross section and the spin observables for different values of the projectile energy. From the comparison with the experimental data and with the results of our previous model we assess the importance of the 3N interaction in the dynamic part of the OP. Conclusions: Our analysis indicates that the contribution of the 3N force in the t matrix is small for the differential cross section and it is sizable for the spin observables, in particular, for the analyzing power. We find that the two-pion exchange term is the major contributor to the 3N force. A chiral expansion order-by-order analysis of the scattering observables confirms the convergence of our results at the next-to-next-to-next-to-leading-order, as already established in our previous work.

Background:In recent years, we constructed a microscopic optical potential (OP) for elastic nucleon-nucleus (NA) scattering using modern approaches based on chiral theories for the nucleon-nucleon (NN) interaction. The OP was derived at first order of the spectator expansion in Watson multiple scattering theory and its final expression was a folding integral between the NN t matrix and the nuclear density of the target. Two-and three-body forces are consistently included both in the target and in the projectile description. Purpose: The purpose of this work is to apply our microscopic OP to nuclei characterized by a ground state of spin-parity quantum numbers J π = 0 + . Methods: We extended our formalism to include the spin of the target nucleus. The full amplitudes of the NN reaction matrix are retained in the calculations starting from two-and three-body chiral forces. Results:The microscopic OP can be applied in the energy range 100 E 350 MeV. We show a remarkable agreement with experimental data for the available observables and, simultaneously, provide reliable estimates for the theoretical uncertainties. Conclusions: This work paves the way toward a full microscopic approach to inelastic NA scattering, showing that the derivation of optical potentials between states with J π = 0 + is completely under control.