New measurement of G_E/G_M for the proton

Abstract

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.