ИСТИНА

Recent experimental progress has led to discovery of multiquark states searched for 50 years since the beginning of QCD. In particular, the first reliable confirmation of existence of six-quark (dibaryon) resonances has been found recently at COSY facility (Juelich). Since the dibaryon resonances are intimately related to the short-range NN interaction and the cross sections of dibaryon production are typically very small, they should be manifested in processes with high momentum transfers, such as meson production in NN and Nd collisions or elastic Nd scattering at large angles. Just for such processes there exist discrepancies between the experimental data and conventional theoretical models for NN and 3N interaction which do not include dibaryon degrees of freedom. In view of all above, study of dibaryon resonances in hadronic and nuclear processes with high momentum transfers becomes of particular importance. New experimental and theoretical evidences of dibaryon resonances in NN system are presented in the talk. Excitation of intermediate dibaryons in the processes of one- and two-pion production in NN collisions is considered. In particular, relative contributions of an intermediate Delta-isobar and isovector dibaryons in the reaction pp -> d pi+ are investigated. Inclusion of dibaryon resonances is shown to considerably improve the description of experimental data for this reaction, provided the consistent parameterization of the pi-N-Delta vertex in pi-N and NN scattering is used. Manifestation of the intermediate isoscalar and isovector dibaryon resonances in the two-pion production processes such as pn -> d pi pi is also studied. The interpretation of the near-threshold enhancement (the so-called ABC-effect) for the above two-pion production reactions in terms of the sigma-dressed isoscalar dibaryon is given. Consequences of intermediate dibaryons production in NN system for Nd elastic and inelastic scattering are also discussed.