Parity violating asymmetries in the Gº experiment: Pion photoproduction on the Δ resonance

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Coppens, Alexandre Francois Constant
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Symmetry tests and more precisely parity violation experiments using the properties of the weak interaction give us unique insight into the internal hadronic structure of matter. The Gº experiment at Jefferson Laboratory used parity violating electron scattering to probe the strange quark contribution to the electromagnetic nucleon form factors, (GMs and GEs) as well as the axial contribution, (GAe). The data taken during the experiment provide further information on the axial transition form factor of the N - $\Delta$ transition, (GANΔ), as well as the scale of the low energy constant (dΔ) characterizing the parity violating γNΔ coupling. The analysis of backward angle Gº data taken with a liquid deuterium target to deduce the parity violating asymmetry for pion photoproduction on the Δ resonance, and the first experimental constraint on the value of dΔ, are reported in this thesis. The results showed that dΔ = (8.3 ± 25.3) gπ where the uncertainty is dominated by statistics, and that 75 percent of the theory range would be excluded by this measurement at 1 sigma.
Delta resonance, Parity Violation, Gº experiment, low energy constant, pion photoproduction, nucleon structure