We derive the sub-subleading two-pion exchange contributions to the three-nucleon force which appear at next-to-next-to-next-to-next-to-leading order in chiral effective field theory. In order to determine the low-energy constants, a complete analysis of pion-nucleon scattering at the subleading-loop order in the heavy-baryon expansion is carried out utilizing the power counting scheme employed in the derivation of the nuclear forces. We discuss the convergence of the chiral expansion for this particular three-nucleon force topology and give the values of the low-energy constants which provide the most realistic description of the three-nucleon force when the chiral expansion is truncated at next-to-next-to-leading order.

The N interaction is studied within a meson-exchange model and in a coupled-channels approach which includes the channels N, N, as well as three effective N channels, namely, N, ⌬, and N. Starting out from an earlier model of the Jülich group systematic improvements in the dynamics and in some technical aspects are introduced. With the new model an excellent quantitative reproduction of the N phase shifts and inelasticity parameters in the energy region up to 1.9 GeV and for total angular momenta Jഛ3/2 is achieved. Simultaneously, good agreement with data for the total and differential N→N transition cross sections is obtained. The connection of the N dynamics in the S 11 partial wave with the reaction N→N is discussed.

A dispersion integral is derived that allows one to relate directly (spin dependent) ΛN invariant mass spectra, measured in a large-momentum transfer reaction such as pp → K + pΛ or γd → K + nΛ, to the scattering length for elastic ΛN scattering. The involved systematic uncertainties are estimated to be smaller than 0.3 fm. This estimate is confirmed by comparing results of the proposed formalism with those of microscopic model calculations. We also show, for the specific reaction pp → K + Λp, how polarization observables can be used to separate the two spin states of the ΛN system.