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New Measurement of Parity Violation in Elastic Electron-Proton Scattering and Implications for Strange Form Factors

Journal Article · · Physics Letters B
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We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The result is A = -15.05 +- 0.98(stat) {+-} 0.56(syst) ppm at the kinematic point theta{sub lab} = 12.3 degrees and Q{sup 2} = 0.477 (GeV/c){sup 2}. The measurement implies that the value for the strange form factor (G{sub E}{sup s} + 0.392 G{sub M}{sup s})/(G{sub M}{sup p} {mu}{sub p}) = 0.069 +- 0.056 +- 0.039, where the first error is experimental and the second arises from the uncertainties in electromagnetic form factors. This measurement is the first fixed-target parity violation experiment that used either a ''strained'' GaAs photocathode to produce highly polarized electrons or a Compton polarimeter to continuously monitor the electron beam polarization.
Research Organization:
Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
Sponsoring Organization:
USDOE Office of Energy Research (ER) (US)
DOE Contract Number:
AC05-84ER40150
OSTI ID:
833901
Report Number(s):
JLAB-PHY-01-75; DOE/ER/40150-2929; nucl-ex/0006002; WM-00-107
Journal Information:
Physics Letters B, Journal Name: Physics Letters B Journal Issue: 3-4 Vol. 509
Country of Publication:
United States
Language:
English