Nucleus as a meson-baryon system

Abstract

We describe the nucleus by a system of mesons ($\ensuremath{\pi},\ensuremath{\rho},\dots{}$) and baryons ($N,{N}^{*},\ensuremath{\Delta},\dots{}$). Starting from a field theoretical Hamiltonian for the composite system we derive a Schr\"odinger equation in a subspace without mesons. In lowest order approximation we obtain a generalization of the one-boson-exchange formulation of the $\mathrm{NN}$ interaction for a general baryon-baryon interaction. We discuss two possible treatments of the many-body system: (i) nucleonic degrees of freedom only, and (ii) explicit inclusion of resonance degrees of freedom. In the case of nucleons and deltas the explicit form of the potentials is given together with a complete new fit of the Reid soft-core potential for the nucleonic part of the interaction. The coupled equations for the scattering states and the deuteron have been solved exactly using the complete baryon-baryon interaction in the one-boson-exchange limit. The deuteron $\ensuremath{\Delta}\ensuremath{\Delta}$ contribution is discussed in several limits of the general one-boson-exchange potential.NUCLEAR STRUCTURE Meson and resonance degrees of freedom, calculated $N\ensuremath{-}N$ scattering, and deuteron properties.