Low Q^2 measurements of the proton form factor ratio $mu_p G_E / G_M$
We present an updated extraction of the proton electromagnetic form factor ratio, {mu}{sub p}G{sub E}/G{sub M}, at low Q{sup 2}. The form factors are sensitive to the spatial distribution of the proton, and precise measurements can be used to constrain models of the proton. An improved selection of the elastic events and reduced background contributions yielded a small systematic reduction in the ratio {mu}{sub p}G{sub E}/G{sub M} compared to the original analysis.
Flavour structure of the nucleon electromagnetic form factors and transverse charge densities in the chiral quark-soliton model
We investigate the flavour decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model ($\chi$QSM) with symmetry-conserving quantisation. We consider the rotational $1/N_c$ and linear strange-quark mass ($m_s$) corrections. We discuss the results of the flavour-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). We finally discuss the transverse charge densities for both unpolarised and polarised nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the centre within the SU(3) $\chi$QSM, which can be explained by the contribution of the strange quark.
New measurement of G_E/G_M for the proton
Recent polarization transfer measurements of the proton form factors disagree with previous Rosenbluth extractions. In addition to providing insight into the proton structure, the form factors also provide crucial input for the analysis of quasielastic experiments, and this discrepancy could have a significant impact on such experiments at moderate-to-large Q^2 values. In 2002, a new ``SuperRosenbluth'' measurement was performed to help understand this origin of this discrepancy, as well its implications on other experiments. Preliminary results agree with previous Rosenbluth extractions, indicating that the discrepancy must be related to some fundamental flaw in either the Rosenbluth or polarization transfer technique.