Effects of chiral three-nucleon forces on ⁴He-nucleus scattering in a wide range of incident energies

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It is a current important subject to clarify properties of chiral three-nucleon forces (3NFs) not only in nuclear matter but also in scattering between finite-size nuclei. Particularly for the elastic scattering, this study has just started and the properties are not understood in a wide range of incident energies (E in). We investigate basic properties of chiral 3NFs in nuclear matter with positive energies by using the Brueckner-Hartree-Fock method with chiral two-nucleon forces of N³LO and 3NFs of NNLO, and analyze effects of chiral 3NFs on ⁴He elastic scattering from targets ²⁰⁸Pb, ⁵⁸Ni and ⁴⁰Ca over a wide range of 30 E in/A P 200 MeV by using the g-matrix folding model, where A P is the mass number of projectile. In symmetric nuclear matter with positive energies, chiral 3NFs make the single-particle potential less attractive and more absorptive. The effects mainly come from the Fujita-Miyazawa 2π-exchange 3NF and slightly become larger as E in increases. These effects persist in the optical potentials of ⁴He scattering. As for the differential cross sections of ⁴He scattering, chiral-3NF effects are large in E in/A P 60 MeV and improve the agreement of the theoretical results with the measured ones. Particularly in E in/A P 100 MeV, the folding model reproduces measured differential cross sections pretty well. Cutoff (Λ) dependence is investigated for both nuclear matter and ⁴He scattering by considering two cases of Λ=450 and 550 MeV. The uncertainty coming from the dependence is smaller than chiral-3NF effects even at E in/A P=175 MeV.