Аннотация
The differential cross section of the reaction pp → {pp} s π0, where {pp} s is the proton pair in the 1S0 state at a small excitation energy E pp < 3 MeV, is calculated using the box diagram with the excitation of the Δ-isobar. The model demonstrates a clear bump observed in the experimental data at the beam energy of ∼0.6 GeV and the zero diproton outgoing angle; however, its absolute value strongly depends on the off-shell extrapolation of the πNΔ vertex factor and underestimates the data.