Proposal to Jefferson Lab PAC 24 Probing the Limits of the Standard Model of Nuclear Physics with the 4He(~e, e′~p)3H Reaction

We propose high precision measurements of the double ratio of polar-ization transfer coefficients, P ′x and P z, of the quasielastic 4He(~e, e′~p) 3H reaction with respect to the elastic 1H(~e, e′~p) reaction, at a Q2 of 0.8 (GeV/c)2 and 1.3 (GeV/c)2. Recently, measurements of this double ratio at both Mainz and JLab hinted at the need to include medium modifi-cations of the proton form factors predicted by a quark-meson coupling model. The proposed experiment would reduce the statistical uncertain-ties in the double polarization ratio at each Q2 by over a factor of two compared to the previous measurement, resulting in roughly equal contri-butions from statistical and systematic uncertainties. These two Q2 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