NNsingle pion production cross sections below 1500 MeV

The isospin reaction cross sections for $\mathrm{NN}$ single pion production are extracted from data for the processes $\mathrm{NN}\to \pi d$ and $\mathrm{NN}\to \mathrm{NN}\pi$. New data in conjunction with older existing data have precisely determined the components of the cross sections for the isospin one ($\mathrm{pp}$) initial state. Other new data for the $\mathrm{np}$ initial state and correct treatment of some older data indicate that the isospin zero reaction cross section is essentially zero below 1000 MeV, which indicates against the presence of inelastic isospin zero $\mathrm{NN}$ resonances.