EuNPC2015

The pion production in proton-proton collisions with formation of the final-state 1S0 proton pair has been studied at ANKE-COSY. The angular dependence of the differential cross section has a forward dip in the whole energy region, its energy dependence reveals a clean peak in the Δ(1232) resonance region. The analyzing power is found significant, the maximal value of its angular dependence varies from 0.3 to 0.8 at different energies. A partial wave analysis assuming essential contribution of only two amplitudes, MPs and MPd, shows a resonance behavior of the d-pion wave amplitude with Breit-Wigner parameters ER = 2181 ± 8 MeV/c2 and Γ = 108 ± 24 MeV/c2. The peak in the forward cross section energy dependence looks as a direct manifestation of a ΔN resonance state in the P-wave of its relative motion. Position of the resonance indicates a strong attractive ΔN interaction in the JP = 2− state. The s-wave transition amplitude has a value comparable with the d-wave amplitude and due to interference causes the observed dip in the forward cross section and significant analyzing power. The s-wave amplitude squared reveals a resonance-like energy dependence similar to that of the d-wave.