Δ-Isobar contribution to the pion production in the reaction pp → {pp}sπ0.

ANKE@COSY data on the cross section of the reaction pp → {pp}_sπ⁰, where {pp}_s is the proton pair in the ¹S₀ state at small excitation energy E_pp = 0 – 3 MeV, obtained at beam energies 0.5 - 2.0 GeV are analyzed within the one-pion exchange model. The model involves the subprocess π⁰p → π⁰p and accounts for the final state pp-interaction. A broad maximum observed in the cross section of the reaction pp → {pp}_sπ⁰ at 0.5 - 1.4 GeV in the forward direction is explained by this model as a dominant contribution of the isospin 3 2 $\cfrac{3}{2}$ in the π⁰p-scattering. The second bump in data at 2 GeV is underpredicted within this model by one order of magnitude. An explicit excitation of the Δ(1232)-isobar using the box-diagram is also considered in the region of the first maximum. [ABSTRACT FROM AUTHOR]