Measurement of the Neutral Pion Lifetime

The QCD chiral anomaly is the dominant contribution to the $\pi ^{0}\to \gamma \gamma $ decay. Therefore, a precision measurement of the $\pi^{0}$ decay width and its comparison with prediction of $\pi^{0}$ lifetime can be used as a test of QCD at the confinement scale. Recent theoretical activities have demonstrated high precision (1{\%} level) calculations of the decay width of the $\pi ^{0}$ into two photons. An experimental determination with comparable precision will be critical to test these predictions. At Jefferson Lab, the PrimEx Collaboration has performed high precision experiments to measure the $\pi^{0}$ lifetime using the Primakoff effect. The first (PrimEx-I) experiment resulted in a published 2.8{\%} total uncertainty in the $\pi^{0}$ decay width. PrimEx-II was carried out in the fall of 2010 with the final goal of 1.4{\%} precision. The preliminary result of this experiment will be presented. This work is supported in part by the US Department of Energy under contract number DE-FG02-03ER41231.