beam energy of 390 MeV

The analyzing power of ~ pp → ppπ0 reaction has been measured at the beam energy of 390 MeV. The missing mass technique of final protons has been applied to iden- tify the π0 production event. The dependences of the analyzing power on the pion emission-angle and the relative momentum of the protons have been obtained. The angular dependence could be decomposed by the Legendre polynomial and the rela- tive contribution of the P21 to P11 function is less than 20%. The P-state amplitude is found to be the dominant component of the π production near the threshold. The momentum dependence of the analyzing power has been studied to obtain the information about the pion production mechanism. It has been deduced that the pion production due to the long range interaction plays an important role in the momentum dependence of the P-state amplitude.