Antinucleon-nucleon interaction at next-to-next-to-next-to-leading order in chiral effective field theory
Abstract
Results for the antinucleon-nucleon ( NN) interaction obtained at next-to-next-to-next-to-leading order in chiral effective field theory (EFT) are reported. A new local regularization scheme is used for the pion-exchange contributions that has been recently suggested and applied in a pertinent study of the NN force within chiral EFT. Furthermore, an alternative strategy for estimating the uncertainty is utilized that no longer depends on a variation of the cutoffs. The low-energy constants associated with the arising contact terms are fixed by a fit to the phase shifts and inelasticities provided by a phase-shift analysis of pp scattering data. An excellent description of the NN amplitudes is achieved at the highest order considered. Moreover, because of the quantitative reproduction of partial waves up to J=3, there is also a nice agreement on the level of pp observables. Specifically, total and integrated elastic and charge-exchange cross sections agree well with the results from the partial-wave analysis up to laboratory energies of 300 MeV, while differential cross sections and analyzing powers are described quantitatively up to 200-250 MeV. The low-energy structure of the NN amplitudes is also considered and compared to data from antiprotonic hydrogen.