Toward dynamical understanding of the diquarks, pentaquarks and dibaryons

Abstract

QCD instantons are known to produce deeply bound diquarks. We study whether it may be used as building blocks in the formation of multiquark states, in particular pentaquarks and dibaryons. A simple model is presented in which the lowest scalar diquark (and possibly the tensor one) can be treated as an independent ``body'', with the same color and (approximately) the same mass as a constituent (anti)quark. In it a new symmetry exists between states with the same number of ``bodies'' but different number of quarks appear, in particular the 3-``body'' pentaquarks can be naturally related to some excited baryons. The limitations of this model are seen from the fact that it leads to light dibaryon $H$. Another reported work is based on a calculation of a large set of correlation functions for nonlocal operators with 4 to 6 light quarks in the Random Instanton Liquid Model (RILM). The effective interaction between diquarks is studied and found to posses a strongly {\em repulsive core}, due to the Pauli principle for quark zero modes.