Experimental Research of Neutral Pion Lifetime

π⁰→γγ decay is dominated by chiral anomaly in quantum chromodynamics(QCD). Based on this anomaly and corrections of chiral perturbation theory(ChPT), π⁰ lifetime is predicted in high precision and the estimated uncertainty is on the level of 1%. The experimental measurement of π⁰ lifetime in a comparable precision is critical to test the QCD and ChPT at confinement scale energy. The methods of π⁰ lifetime measurement and experiments included in PDG of 2018 version for π⁰ lifetime average are reviewed, in which PrimEx-I performed in JLab in 2004 is the most precise experiment and has a total uncertainty of 2.8%. Even though those experimental results are in agreement with theoretical prediction in the range of experimental errors, the precision is not yet sufficient totri sngently test the theoretical prediction. In order to get more precise measurement of π⁰ lifetime, PrimEx-II was performed in JLab in 2010 with the precision of 1.57%. The weighted average of PrimEx-I and PrimEx-II results has a total uncertainty of 1.50% and confirms the prediction based on the chiral anomaly in QCD. Moreover, the experiment setup and data analysis approach of PrimEx-II are also reviewed in this article.