A Precision Measurement of the Neutral Pion Lifetime Via the Primakoff Effect

The neutral pion lifetime is arguably the most precise theoretical calculation possible in low energy QCD, but the current world data are not commensurate with theory. Recent calculations predict a neutral pion radiative width of 8.1 eV $\pm$ 1\%, while the PDG average stands at 7.84 eV $\pm$ 7\%. The Primakoff Experiment (PrimEx) collaboration has utilized the Primakoff effect, photo-meson production in the Coulomb field of nuclei, to generate neutral pions. PrimEx collected data in Hall B at the Thomas Jefferson National Accelerator Facility with the expectation of measuring the neutral pion lifetime to an accuracy of 1.5\%. Results of this measurement will be presented. This result is a stringent test of the U(1) axial anomaly, and thus fills an important gap in our knowledge of low energy QCD.