Polarization transfer in wide-angle charged pion photoproduction: Experiment overview and analysis status

Single pion photoproduction from a nucleon is one of the simplest inelastic hadronic processes. Understanding the mechanism behind this interaction would be a groundbreaking development. In the spring of 2024, the Super Bigbite Spectrometer (SBS) collaboration performed a first measurement of the polarization transfer observables K_LL , K_LS for the reaction γn → π^-p, at sufficiently large values of the Mandelstam variables s, t, u, to test the predictions of GPD-based calculations requiring twist-3 dominance of the scattering amplitude to account for the measured cross sections. The measurement used the SBS to detect and measure the polarization of recoiling protons, and the Bigbite Spectrometer to detect the π^- in coincidence to suppress backgrounds. The experiment used 6.4 GeV polarized electrons from CEBAF on a 6% Cu radiator to generate an intense beam of polarized Bremsstrahlung photons in the energy range of 4 – 6 GeV incident on a 15-cm liquid deuterium target. In this talk I will give a brief summary of the theory and motivations behind the experiment and present an overview of the current progress of the data analysis.