Realistic two-baryon potential coupling two-nucleon and nucleon-Δ-isobar states: Fit and applications to three-nucleon system

A two-baryon coupled-channel potential is developed. It couples two-nucleon states and states in which one nucleon is turned into a Δ isobar. It is developed as extension of the purely nucleonic charge-dependent (CD) Bonn potential. It is fitted to two-nucleon scattering data up to 350 MeV nucleon lab energy. Since scattering energies just touch the pion-production threshold, the Δ isobar is considered a stable baryon. The resulting fit of the coupled-channel potential is of the same quality as that for CD Bonn. The coupled-channel potential is as realistic as CD Bonn and as any other modern two-nucleon potential. It is charge-dependent as CD Bonn. It is employed for the description of elastic and inelastic three-nucleon scattering. The Δ isobar yields an effective three-nucleon force in the three-nucleon system, besides other effects. Δ-isobar effects in three-nucleon scattering are isolated and discussed