Precision measurement of the proton neutral weak form factors at Q(2) ~ 0.1 GeV(2)
Abstract (Summary)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 [left angle bracket][straight theta]lab [right angle bracket] = 6Â°. 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 Â± 0.24 (stat) Â± 0.06 (syst) ppm at [left angle bracket]Q 2 [right angle bracket] = 0.099 GeV2 (2004), and APV = -1.58 Â± 0.12 (stat) Â± 0.04 (syst) ppm at [left angle bracket]Q 2 [right angle bracket] = 0.109 GeV2 (2005). The strange quark form factors extracted from the asymmetry are [Special characters omitted.] + 0.080[Special characters omitted.] = 0.030 Â± 0.025 (stat) Â± 0.006 (syst) Â± 0.012 (FF) (2004) and [Special characters omitted.] + 0.088[Special characters omitted.] = 0.007 Â± 0.011 (stat) Â± 0.004 (syst) Â± 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.
School Location:USA - Massachusetts
Source Type:Master's Thesis
Date of Publication:01/01/2007