Electric Form Factor of the Neutron

Recent polarization-based precision measurements of the nucleons' elastic electric form factors have led to surprising results. The measurement of the ratio of the proton's electromagnetic form factors, μp GEp/GMp, was found to drop nearly linearly with Q2 out to at least 5 GeV2, inconsistent with the older Rosenbluth-type experiments. A recent measurement of GEn, the neutron's electric form-factor saw GEn does not fall off as quickly as commonly expected up to Q2 ∼ 1.5 GeV2. Extending this study, a precision measurement of GEn up to Q2=3.5 GeV2 was completed in Hall A at Jefferson Lab. The ratio GEn/GMn was measured through the beam-target asymmetry A#perpendicular# of electrons quasi-elastically scattered off polarized neutrons in the reaction (3(rvec H)e(rvec e),e(prime)n). The experiment took full advantage of the electron beam, recent target developments, as well as two detectors new to Jefferson Lab. The measurement used the accelerator's 100% duty-cycle high-polarization (typically 84%) electron beam and a new, hybrid optically-pumped polarized 3(rvec H)e target which achieved in-beam polarizations in excess of 50%. A medium acceptance (80msr) open-geometry magnetic spectrometer (BigBite) detected the scattered electron, while a geometrically matched neutron detector observed the struck neutron. Preliminary results from this measurement will be discussed and compared to modern calculations of GEn.