Measurements of the electromagnetic form factor of the Proton at JLab · arXivDesk
nucl-ex/0307001Jun 30, 200310 pages, 6 figures, presented at Xth International Seminar on Electromagnetic Interactions of Nuclei at Low and Medium Energies, INP, RAS, Moscow, 16-18 April, 2003, will appear in the proceedings
Measurements of the electromagnetic form factor of the Proton at JLab
Vina Punjabi, Charles Perdrisat, Jefferson Lab Hall A Collaboration, GEp-III Collaboration
The ratio of the proton's elastic electromagnetic form factors GEp/GMp was obtained by measuring Pt
Nearby in the stack
and
Pℓ
, the transverse and longitudinal recoil proton polarization, respectively. For the elastic reaction
ep→ep
,
GEp/GMp
is proportional to
Pt/Pℓ
. The simultaneous measurement of
Pt
and
Pℓ
in a polarimeter reduces systematic uncertainties. The results for the ratio
GEp/GMp
measured in Hall A so far show a systematic decrease with increasing
Q2
, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. Together these experiments cover the Q
2
- range of 0.5 to 5.6 GeV
2
. A new experiment is currently being prepared, to extend the Q