The Parity-Violating Asymmetry in the N→∆ Transition at Very Low Q²

The main focus of the Q_weak experiment at Jefferson Lab is the recently published determination of the proton’s weak charge. In order to make corrections to the measured asymmetry at low Q² due to inelastically scattered electrons, dedicated measurements were made of the parity violating asymmetry in the N→∆ transition at two different beam energies (877 MeV and 1.16 GeV). The measured inelastic asymmetries are used to extract the low energy constant d_Δ, which is an additional physics result. The low energy constant d_Δ results in a non-zero asymmetry at photon point (Q² = 0), and is recognized as the parity violating hadronic excitation in the N→∆ transition. This has been known to be relevant to some puzzles in radiative hyperon decays. Theoretical analyses indicate potential values of d_Δ much greater than its natural scale. By using the Q_weak apparatus, two beam energies 877 MeV (Q² = 0.01 GeV²) and 1.16 GeV (Q² = 0.02 GeV²) were used in this experiment. Inelastic measurement motivations, further analysis, and preliminary results for these measurements will be presented.