Precision measurement of the proton neutral weak form factors at squared momentum transfer ~ 0.1 GeV(2)
This thesis reports the HAPPEX measurement of the parity-violating asymmetry for longitudinally polarized electrons elastically scattered from protons in a liquid hydrogen target. The measurement was carried out in Hall A at Thomas Jefferson National Accelerator Facility using a beam energy E = 3 GeV and scattering angle ⟨&thetas;lab⟩ = 6°. The asymmetry is sensitive to the weak neutral form factors from which we extract the strange quark electric and magnetic form factors ([special characters omitted] and [special characters omitted]) of the proton. The measurement was conducted during two data-taking periods in 2004 and 2005. This thesis describes the methods for controlling the helicity-correlated beam asymmetries and the analysis of the raw asymmetry. The parity-violating asymmetry has been measured to be APV = -1.14 ± 0.24 (stat) ± 0.06 (syst) ppm at ⟨Q 2⟩ = 0.099 GeV2 (2004), and APV = -1.58 ± 0.12 (stat) ± 0.04 (syst) ppm at ⟨Q 2⟩ = 0.109 GeV2 (2005). The strange quark form factors extracted from the asymmetry are [special characters omitted] + 0.080[special characters omitted] = 0.030 ± 0.025 (stat) ± 0.006 (syst) ± 0.012 (FF) (2004) and [special characters omitted] + 0.088[special characters omitted] = 0.007 ± 0.011 (stat) ± 0.004 (syst) ± 0.005 (FF) (2005). These results place the most precise constraints on the strange quark form factors and indicate little strange dynamics in the proton.