A schematic model for pentaquarks based on diquarks

QCD instantons are known to produce deeply bound diquarks which may be used as building blocks in the formation of multiquark states, in particular, pentaquarks and dibaryons. We suggest a simple model 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 mass as a constituent (anti)quark. In this model a new symmetry 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 decuplet baryons. We estimate both the masses and widths of such states, and then discuss the limitations of this model. (C) 2004 Published by Elsevier B.V.