Optical potentials derived from nucleon-nucleon chiral potentials at N4LO

Background: Elastic scattering is probably the main event in the interactions of nucleons with nuclei. Even if
this process has been extensively studied in the past years, a consistent description, i.e., starting from microscopic
two- and many-body forces connected by the same symmetries and principles, is still under development.
Purpose: In a previous paper [M. Vorabbi, P. Finelli, and C. Giusti, Phys. Rev. C 93, 034619 (2016)] we derived
a theoretical optical potential from N N chiral potentials at fourth order (N 3 LO). In the present work we use N N
chiral potentials at fifth order (N 4 LO), with the purpose to check the convergence and to assess the theoretical
errors associated with the truncation of the chiral expansion in the construction of an optical potential.
Methods: Within the same framework and with the same approximations as the previous paper [M. Vorabbi,
P. Finelli, and C. Giusti, Phys. Rev. C 93, 034619 (2016)], the optical potential is derived as the first-order
term within the spectator expansion of the nonrelativistic multiple scattering theory and adopting the impulse
approximation and the optimum factorization approximation.
Results: The pp and np Wolfenstein amplitudes and the cross section, analyzing power, and spin rotation of
elastic proton scattering from 16 O, 12 C, and 40 Ca nuclei are presented at an incident proton energy of 200 MeV.
The results obtained with different versions of chiral potentials at N 4 LO are compared.
Conclusions: Our results indicate that convergence has been reached at N 4 LO. The agreement with the
experimental data is comparable with the agreement obtained in the previous paper [M. Vorabbi, P. Finelli,
and C. Giusti, Phys. Rev. C 93, 034619 (2016)]. We confirm that building an optical potential within chiral
perturbation theory is a promising approach for describing elastic proton-nucleus scattering.