Roles of chiral three-nucleon forces in nucleon-nucleus scattering

We investigate the effects of chiral three-nucleon force (3NF) at NNLO level on nucleon-nucleus (NA) elastic scattering, using the standard framework based on the Brueckner-Hartree-Fock method for nuclear matter and the g-matrix folding model for NA elastic scattering. The optical potential in nuclear matter calculated from chiral two-nucleon force (2NF) at N³LO level is found to be close to that from Bonn-B 2NF, whereas the Melbourne g-matrix is known as a practical effective nucleon-nucleon interaction constructed by localizing the g-matrices calculated from Bonn-B 2NF. As the first attempt to estimate chiral-3NF effects on NA scattering, the effects are simply introduced by multiplying the local Melbourne g-matrix by the ratio of the optical potential in nuclear matter calculated from chiral 2NF+3NF to that from chiral 2NF. For NA elastic scattering on various targets at 65 MeV, chiral 3NF makes the folding potential less attractive and more absorptive. The novel property for the imaginary part is originated in the enhancement of tensor correlations due to chiral 3NF (mainly the 2π-exchange diagram). The two effects are small for differential cross sections and vector analyzing powers at the forward and middle angles where the experimental data are available. If backward measurements are made, the data will reveal the effects of chiral 3NF.