The electric form factor of the neutron at low momentum transfers as measured at Bates Large Acceptance Spectrometer Toroid

Elastic form factors are characteristic signatures of the electromagnetic properties of hadronic matter. The more precisely we can measure these values, the more powerful becomes the predictability of our theory.; The proton's form factors ( GpE,GpM ) have been measured remarkably well compared to the neutron. While the Magnetic form factor of the neutron is reasonably well known, the Electric Form Factor still retains difficulties due to its small magnitude and the relative inefficiency of detecting neutral particles. The lack of a pure neutron source is another obstacle.; Although we are in pursuit of the elastic form factors, the two-nucleon system of deuterium has been shown to be a worthy target for extracting data on the structure of nucleons as well as properties of few-body hadronic systems. Data from unpolarized cross section measurements have proven insufficient for extracting GnE , but polarized scattering from a polarized Deuterium target has been shown to be well suited for determination of GnE . The double polarization observables of a vector polarized Deuterium target and polarized electron beam is proportional to the product of the electric and magnetic form factors of the neutron.; The Bates Large Acceptance Spectrometer Toroid (BLAST) has been developed specifically to measure the scattering of a polarized electron beam off a vector and tensor polarized deuterium target and thus fulfills our needs for extracting GnE . The Bates accelerator provides a high-duty polarized electron beam stored in the South Hall Ring (SHR) that is passing through an internal target of both vector and tensor polarized monatomic deuterium as well as polarized monatomic hydrogen provided by an Atomic Beam Source (ABS). A large acceptance detector, BLAST, has been installed to measure several scattering reactions including the directly applicable H2&ar; e&ar;,e'n p reaction.; This work summarizes the experimental investigations of the extraction of GnE from the BLAST data. Points were extracted at four values of four-momentum transfers (Q2 = 0.14, 0.20, 0.29, 0.41 GeV 2). The world's data and the new BLAST data were fit to determine GnE to +/-5.8% from 0 < Q2 < 1.8 GeV2. The best fit includes model dependent contributions from a low Q2 bump and a smooth dipole term. A second fit is shown using a model independent sum of gaussians in order to provide a more reliable determination of the uncertainty of the world's measurement of GnE from double polarized scattering.