Nature of $$\varvec{S}$$S -wave $$\varvec{NN}$$NN interaction and dibaryon production at nucleonic resonance thresholds

Phase shifts and inelasticity parameters for NN scattering in the partial-wave channels $${}^3S_1$$ – $${}^3D_1$$ and $${}^1S_0$$ at energies $$T_\mathrm{lab}$$ from zero to about 1 GeV are described within a unified NN potential model assuming the formation of isoscalar and isovector dibaryon resonances near the $$NN^*(1440)$$ threshold. Evidence for these near-threshold resonances is actually found in the recent WASA experiments on single- and double-pion production in NN collisions. There, the excitation of the Roper resonance $$N^*(1440)$$ exhibits a structure in the energy dependence of the total cross section which corresponds to the formation of dibaryon states with $$I(J^\pi )=0(1^+)$$ and $$1(0^+)$$ at the $$NN^*(1440)$$ threshold. These two S-wave dibaryon resonances may provide new insight into the nature of the strong NN interaction at low and intermediate energies.