³He and ³H Mirror Nuclei Elastic Cross Sections

The cross-section for elastic electron-nucleus scattering from a spin-1/2 particle is described by two nuclear form factors, fundamental quantities that describe the electromagnetic structure of the nucleus. By going to low energy and forward angle, the effect of the magnetic form factor G_M(Q²) can be minimized, which allows for an extraction of the charge form factor GE(Q²)  without having to do a Rosenbluth type experiment. The RMS charge radius of the nucleus is proportional to the slope, dGE(Q²)  as Q²​​​​​​​ --> 0, so by measuring the electric form factor of a target at low Q²​​​​​​​ , we can extrapolate and extract the nucleus charge radius.

The primary aim of my work is the extraction of the elastic cross-section from data collected in Jefferson Lab Hall A experiment E12-11-112 which measured elastic scattering from the mirror nuclei ³He and ³H at low momentum transfer  Q²​​​​​​​ = 0.11 GeV². I determined the ratio of the  ³He and ³H elastic data since it cancels many systematic uncertainties that enter into the absolute cross-section extraction. These new results will be used to improve global fits that examine the difference between the ³He and ³H charge radii.   In particular, these results will help fit the normalization of previous elastic tritium measurement and thus will dramatically improve the global fit.