The isoscalar cross section of one pion production in NN interactions is discussed. The difference between the cross section of single pion production with a mixed symmetry and the isovector cross section were obtained from the experimental data. In the energy dependence of the isoscalar cross section, a resonance-like structure is observed with a maximum at s = 2310 MeV and a width of 150 MeV.
Doroshkevich et al. (Mon,) studied this question.