Constituent Quark Model and nucleon-Nucleon Potentials

Th. A. Rijken

Published 2024-12-25Version 1

In these notes, while focusing on the meson-nucleon vertices, we give a derivation of the nucleon-nucleon 9NN) potentials from meson-exchange between quarks. To establish such a relation the quark-quark-meson (QQM) interactions are properly defined. Hitherto, the coefficients in the Pauli-spinor expansion of the meson-nucleon-nucleon (NNM) vertices are equated with those of the QQM-vertices. In these notes we employ the description of the nucleon with Dirac-spinors in the SU(6) semi-relativistic "constituent" quark-model (CQM) as formulated by LeYouanc, et al. It appears that the constituent quark model with $m_q= M_N/3$, is able to produce the same ratio's for the central-, spin-spin-, tensor-, spin-orbit-, and quadratic-spin-orbit Pauli-invariants as in the phenomenological NNM-vertices. In order to achieve this, the scalar-, magnetic-vector, and axial-vector interactions require, besides the standard ones, an extra coupling to the quarks without the introduction of new parameters. in the case of the axial-vector mesons an extra coupling to the quarks is necessary, which is related to the quark orbital angular momentum contribution to the nucleon spin. Furthermore, a momentum correlation between the quark that is coupled to the meson and the remaining quark pair, and a (gaussian) QQM form factor, are necessary to avoid "spurious" terms. From these results we have obtained a formulation of the QQ-interactions which is directly related to the NN extended-soft-core (ESC) interactions. This has been applied to mixed quark-nuclear matter in a study of (heavy) neutron stars.