The neutron charge form factor at low Q²

Measurement of the charge form factor of the neutron G_E ⁿ presents a sensitive test of nucleon models and QCD-inspired theories. In particular, the pion cloud is expected to play a dominant role in the low-momentum transfer region of G_Eⁿ. At the MIT-Bates Linear Accelerator Center, G_Eⁿ has been measured by means of (e,e') quasielastic scattering of polarized electrons from vector-polarized deuterium. The experiment used the longitudinally polarized stored electron beam of the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic deuterium target provided by an atomic beam source. The measurements have been carried out with the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST) with enhanced neutron detection capability. From the beam-target double polarization asymmetry with the target spin oriented perpendicular to the momentum transfer the form factor G _Eⁿ is extracted over a range of four-momentum transfer Q² between 0.12 and 0.70 (GeV/c)² with minimized model dependencies.