Instantons and $\eta$ Meson Production near threshold in NN collisions

Abstract

An enhancement for the $\eta$ production in proton-neutron collisions as compared with that in proton-proton scattering has been recently observed. We present a calculation for the production cross section, in proton-neutron collisions near threshold, within instanton model for the QCD vacuum and show that a specific flavor dependent nonperturbative quark-gluon interaction related to instantons is able to explain the observed enhancement.

Comments: 11 pages, latex, 3 figures, revised version, footnotes have been added, the notation of two formulas slightly changed, and conclusions enlarged