Is there diquark clustering in the nucleon?

Abstract

It is shown that the instanton-induced interaction in $\mathrm{qq}$ pairs, iterated in the t channel, leads to a meson-exchange interaction between quarks. In this way one can achieve a simultaneous understanding of low-lying mesons, baryons, and the nuclear force. The discussion is general and does not necessarily rely on the instanton-induced interaction. Any nonperturbative gluonic interaction between quarks, which is a source of the dynamical chiral symmetry breaking and explains the $\ensuremath{\pi}\ensuremath{-}\ensuremath{\rho}$ mass splitting, will imply an effective meson exchange picture in the baryons. Because of the (anti)screening there is a large difference between the initial 't Hooft interaction and the effective meson-exchange interaction. It is demonstrated that the effective meson-exchange interaction, adjusted to the baryon spectrum, does not bind the scalar diquark and does not induce any significant quark-diquark clustering in the nucleon because of the nontrivial role played by the Pauli principle.