Form Factors in Electron-Trinucleon Scattering

Abstract

We analyze the four form factors in electron-trinucleon ($e$-${\mathrm{H}}^3$ or $e$-${\mathrm{He}}^3$) elastic scattering using two alternative sets of four unknowns: (i) the neutron electric form factor, the form factor $F_1$ for the dominant $S$ state, and the isovector- and isoscalar-exchange magnetic form factors—here we neglect the mixed symmetry $S^{\prime }$ state; (ii) the form factors $F_O$ and $F_L$ for odd and like nucleons, and the isovector- and isoscalar-exchange magnetic form factors—here we assume knowledge of the neutron electric form factor, essentially 0.02 $q^2$ in our region. The first alternative gives positive neutron electric form factors that seem somewhat high; the second alternative gives a plausible value of 1% for the probability of the mixed-symmetry $S^{\prime }$ state, and also gives a reasonable shape for the isovector-exchange form factor. The isoscalar-exchange form factor stays less than 0.06 nm. We find good agreement between our results for $F_1$ and calculations based on three different wave functions adjusted to give the experimental Coulomb energy.