Date of Award
Doctor of Philosophy (PhD)
Qweak has used the parity violating asymmetry to test the Standard Model (SM) by constantly flipping helicity states of a longitudinally polarized electron beam that scatters in the unpolarized LH2 target. The main focus of the Qweak experiment at Jefferson Lab was the recently published determination of the proton’s weak charge. In order to make corrections to the measured asymmetry at low 𝑄 2 due to inelastically scattered electrons, dedicated measurements were made of the parity violating asymmetry in the N→∆ transition at two different beam energies.
The measured inelastic asymmetries are used to extract the low energy constant dΔ, which is an additional physics result. The low energy constant dΔ results in a non-zero asymmetry at photon point (𝑄 2 = 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∆ much greater than its natural scale. By using the Qweak apparatus, the parity violating asymmetry in the N→∆ transition at 𝑄 2 = 0.02 GeV2 was extracted to be Ainel,total = − 3.91 ± 0.80 (𝑠𝑡𝑎𝑡) ± 1.27 (𝑠𝑦𝑠𝑡) 𝑝𝑝𝑚, which constrains the low energy constant to be 𝑑∆ = ( 26 ± 18 (𝑠𝑡𝑎𝑡) ± 29 (𝑠𝑦𝑠𝑡) ± 3 (𝑡ℎ𝑒𝑜𝑟𝑦)) 𝑔𝜋 . Inelastic measurement motivations, further analysis, and preliminary results for these measurements will be presented in this dissertation.
Alshayeb, Thamraa A., "" (2020). Dissertation. 857.