Measurements of charged pion and neutral pion electromagnetic polarizabilities at GlueX*

Electromagnetic polarizabilities are fundamental properties of composite systems such as molecules, atoms, nuclei and hadrons, with polarizabilities being sensitive to the 'stiffness' of the system and the spectrum of excited states. Measurements of hadron polarizabilities provide a test of effective field theories, dispersion theories, and lattice calculations, and the charged pion polarizability tests fundamental symmetries at leading order. While significant progress has been made in measurements of nucleon polarizabilities, with uncertainties  ≅ ± 0.4 x 10^-4 e fm³ for the proton, experimental constraints on the charged and neutral pion polarizabilities (CPP and NPP) are much weaker, ≅ ± 2 x 10^-4 e fm³ for the charged pion and no measurement for the neutral pion. The upcoming CPP and NPP experiments at GlueX utilize a new technique to measure pion polarizability, Primakoff photo-production of π⁺π^- and π⁰π⁰ pairs on a high Z target. Details of the technique and experimental setup will be presented in the talk, including the commissioning of a muon detection system constructed for the measurement.  The CPP and NPP experiments are scheduled to run at JLab in mid-2022.