Precision Measurement of the proton neutral weak form factors at Q² ~ 0.1 GeV²

Thesis/Dissertation · Thu Feb 01 04:00:00 EST 2007

DOI:https://doi.org/10.2172/1054071· OSTI ID:1054071

Kaufman, Lisa J. ^[1]

---

1. Univ. of Massachusetts, Amherst, MA (United States)

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 <θ{sub lab}> = 6°. The asymmetry is sensitive to the weak neutral form factors from which we extract the strange quark electric and magnetic form factors (G$$s\atop{E}$$ and G$$s\atop{M}$$) 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 A_PV = -1.14± 0.24 (stat)±0.06 (syst) ppm at 2> = 0.099 GeV² (2004), and A_PV = -1.58±0.12 (stat)±0.04 (syst) ppm at 2> = 0.109 GeV² (2005). The strange quark form factors extracted from the asymmetry are G$$s\atop{E}$$ + 0.080G$$s\atop{M}$$ = 0.030 ± 0.025 (stat) ± 0.006 (syst) ± 0.012 (FF) (2004) and G$$s\atop{E}$$ +0.088G$$s\atop{M}$$ = 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.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Energy Research (ER)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 1054071
• Report Number(s): JLAB-PHY--07-1010; DOE/OR/23177--2358
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS