Analyzing power of the reaction pp→ppπ⁰ at a beam energy of 390 MeV

The analyzing power of the reaction pp→ppπ⁰ has been measured at a beam energy of 390 MeV. The dependences of the analyzing power on the pion emission-angle and the relative momentum of two outgoing protons have been obtained. The angular dependence could be decomposed by Legendre polynomial and the relative contribution of the P₂₁ to the P₁₁ function is less than 4%. The momentum dependence of the analyzing power has been studied to obtain information about the pion-production mechanism. It has been deduced that pion production due to the long-range interaction plays an important role in the momentum dependence of the P-state amplitude.