Is there diquark clustering in the nucleon?

Abstract

It is shown that the instanton-induced interaction in qq pairs, iterated in t-channel, leads to a meson-exchange interactions 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 $\pi$ - $\rho$ mass splitting, will imply an effective meson exchange picture in baryons. Due to the (anti)screening there is a big 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.

Comments: Final version to appear in Phys. Rev. D; typos have been corrected; some formulae have been written in a more detailed form; some references have been updated