Charged Pion Polarizability from Primakoff Photo-Production of π⁺π^- on a Lead Target at Jefferson Lab

The Charged Pion Polarizability (CPP) experiment at Jefferson Lab is a precision measurement of the pion electromagnetic polarizability using the GlueX detector. The electromagnetic polarizability is a fundamental property of particles that provides a test of effective field theories, dispersion theories, and lattice calculations. In contrast to past experiments of this measurement, the CPP experiment utilizes a new technique to measure the pion polarizability,Primakoff photo-production of  π⁺π^- pairs on a lead target at 6 GeV incident photon energy, where the forward kinematics are dominated by the process γγ → π⁺π^-. A dedicated muon detector system was added to the GlueX apparatus, in tandem with a machine-learning based particle-identification algorithm to separate π⁺π^- from e⁺e^- and μ⁺μ^- backgrounds. This approach uses a neural network classifier known as a multi-layer perceptron with performance evaluated over physics distributions relevant for the Primakoff selection region. Preliminary measurements of key physics observables will be presented along with a strategy for an amplitude analysis to extract γγ → π⁺π^- cross sections from the Primakoff contribution.