Proposal to Jefferson Lab PAC 23 Probing the Limits of the Standard Model of Nuclear Physics with the 4 He ( e , e ′ p ) 3 H Reaction

We propose high precision measurements of the double ratio of polarization transfer coefficients, P ′ x and P ′ z, of the quasielastic He( e, e′ p ) H reaction with respect to the elastic H( e, e′ p ) reaction, at a Q of 0.8 (GeV/c) and 1.3 (GeV/c). Recently, measurements of this double ratio at both Mainz and JLab hinted at the need to include medium modifications of the proton form factors predicted by a quark-meson coupling model. The proposed experiment would reduce the statistical uncertainties in the double polarization ratio at each Q by over a factor of two compared to the previous measurement, resulting in roughly equal contributions from statistical and systematic uncertainties. These two Q values were selected since they lie in a region where theoretical calculations are expected to be reliable. This measurement would provide one of the most stringent tests to date of the applicability of conventional meson-nucleon calculations. 1 Physics Motivation