Constraints on the Nucleon Strange Form Factors at Q{sup 2} {approx} 0.1 GeV{sup 2}
We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle <{theta}{sub lab}> = 6.0 degrees, with the result A{sub PV} = -1.14 {+-} 0.24 (stat) {+-} 0.06 (syst) parts per million. From this we extract, at Q{sup 2} = 0.099 GeV{sup 2}, the strange form factor combination G{sub E}{sup s} + 0.080 G{sub M}{sup s} = 0.030 {+-} 0.025 (stat) {+-} 0.006 (syst) {+-} 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. The measurement significantly improves existing constraints on G{sub E}{sup s} and G{sub M}{sup s} at Q{sup 2} {approx}0.1 GeV{sup 2}. A consistent picture emerges from all measurements at this Q{sup 2}. A combined fit shows that G{sub E}{sup s} is consistent with zero while G{sub M}{sup s} prefers positive values though G{sub E}{sup s} = G{sub M}{sup s} = 0 is compatible with the data at 95% C.L.
- 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:
- 841463
- Report Number(s):
- JLAB-PHY-05-313; DOE/ER/40150-3458; nucl-ex/0506011; TRN: US0502600
- Resource Relation:
- Other Information: No journal information given for this preprint; PBD: 1 Jun 2005
- Country of Publication:
- United States
- Language:
- English
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