Parity Violation in Forward Angle Elastic Electron-Proton Scattering

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 2001

DOI:https://doi.org/10.2172/883372· OSTI ID:883372

Miller, IV, Grady Wilson ^[1]

---

1. Princeton Univ., NJ (United States)

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton at Jefferson Laboratory. The kinematic point (θ_lab = 12.3 deg. and (Q²) = 0.48 (GeV/c)²) is chosen to provide sensitivity to the strange electric form factor G^s_E. A 3.36 GeV beam of longitudinally polarized electrons was scattered from protons in a liquid hydrogen target. The scattered flux was detected by a pair of spectrometers which focussed the elastically-scattered electrons onto total-absorption detectors. The detector signals were integrated and digitized by a custom data acquisition system. A feedback system reduced systematic errors by controlling helicity-correlated beam intensity differences at the sub-ppm (part per million) level. The experimental result, A = 14.5 +/- 2.0 (stat) ± 1.1 (syst) ppm, is consistent with the electroweak Standard Model with no additional contributions from strange quarks. In particular, the measurement implies G^S_E + 0.39 G^s_M = 0.023 ± 0.040 ± 0.026 (ζGⁿ_E), where the last uncertainty is due to the estimated uncertainty in the neutron electric form factor Gⁿ_E . This result represents the first experimental constraint of the strange electric form factor.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Energy Research (ER)
• DOE Contract Number: AC05-84ER40150
• OSTI ID: 883372
• Report Number(s): JLAB-PHY--01-106; DOE/ER/40150--3922
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS