Hidden dibaryons in one- and two-pion production in NN collisions

Processes of one- and two-pion production in NN   collisions are considered in connection with excitation of intermediate dibaryon resonances. In particular, relative contributions of the conventional meson-exchange and dibaryon excitation mechanisms in the reaction pp→dπ+pp→dπ+ are investigated in detail. Inclusion of the intermediate isovector dibaryon resonances is shown to essentially improve the description of experimental data for this reaction, provided the soft meson–baryon form factors consistent with πN   elastic scattering are used. Manifestation of the intermediate isoscalar and isovector dibaryons in the two-pion production processes is also studied. The role of the isovector dibaryon resonances in the reaction pp→ppππpp→ppππ is discussed for the first time. An explanation of the observed strong differences between two-pion production cross sections in pn and pp collisions based in part on the analysis of dibaryon structure is suggested.