Measurement of the proton's G{sub Ep}/G{sub Mp} ratio to Q{sup 2} = 5.6 GeV{sup 2} at Jlab
The ratio of the electric and magnetic proton form factors, G{sub Ep}/G{sub Mp}, has been studied in the Thomas Jefferson National Accelerator Facility (Hall) A at JLab in two experiments, from measurements of the longitudinal and transverse polarization of the recoil proton, P{sub l} and P{sub t}, respectively, in the elastic scattering of polarized electrons, {rvec e}p {yields} e{sup {rvec p}}. Together, these experiments cover the Q{sup 2}-range 0.5 to 5.6 GeV{sup 2}. The results of the second experiment are discussed here; although preliminary, they confirm and extend the finding of the first experiment, that the ratio {mu}{sub p}G{sub Ep}/G{sub Mp}, which is close to 1 for Q{sup 2} < 0.8 GeV{sup 2}, decreases approximately linearly with Q{sup 2} above this momentum transfer squared, and reaches a value {approx} 0.19 at Q{sup 2} = 5.6 GeV{sup 2}. The new results presented here have been obtained by measuring the recoil proton polarization in {rvec e}p {yields} e{sup {rvec p}}, which provides a better way to obtain G{sub Ep}, even in the presence of a dominant magnetic form factor. Precision measurements of polarization observables have become possible with the advent of polarized electron beams with {approx} 100% duty factor, high current and high polarization.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 839085
- Report Number(s):
- JLAB-PHY-01-98; DOE/ER/40150-3306; TRN: US0501619
- Resource Relation:
- Conference: International Nuclear Physics Conference (INPC 2001): Nuclear Physics and the 21st Century, Berkeley, CA (US), 07/30/2001--08/03/2001; Other Information: PBD: 1 Apr 2002
- Country of Publication:
- United States
- Language:
- English
Similar Records
Proton Elastic Form Factor Ratio: the JLab Polarization Experiments
Experimental search for two-hard-photon exchange in elastic ep experiments