Single Spin Asymmetry of Neutral Pion at 200 GeV Polarized p+p Colisions

To understand the nuclear spin structure function, the single spin asymmetry ofπ⁰ produced in collision of polarized proton was researched. The single spin asymmetry of π⁰, produced in polarized proton-proton collisions at 200 GeV, has been drawn from RHIC Run8 data, which covers a p_T range of 1-7 GeV/c. Due to the higher rates and the higher beam polarization, the preliminary result is smaller with 3 orders of magnitude than Run2. This phenomenon implies a constraint of the Sivers distribution of gluons calculated by pQCD theory.