JLab Measurement of the $^4$He Charge Form Factor at Large Momentum Transfers

The electromagnetic (EM) form factors of the heliumisotopes are, along with the deuteron and tritium formfactors, the \observables of choice" [1] for testing thenucleon-meson standard model of the nuclear interac-tion and the associated EM current operator [2]. Theyprovide fundamental information on the internal struc-ture and dynamics of the light nuclei as they are, in asimple picture, convolutions of the ground state wavefunction with the EM form factors of the constituentnucleons. The theoretical calculations for these few-body observables are very sensitive to the model used forthe nuclear EM current operator, especially its meson-exchange-current (MEC) contributions. Relativistic cor-rections and possible admixtures of multi-quark states inthe nuclear wave function might also be relevant [2]. Ad-ditionally, at large momentum transfers, these EM formfactors may o er a unique opportunity to uncover a pos-sible transition in the description of elastic electron scat-tering on few-body nuclear systems, from meson-nucleonto quark-gluon degrees of freedom, as predicted by quark-dimensional scaling [3, 4].Experimentally, the few-body form factors are deter-mined from elastic electron-nucleus scattering studies us-ing high intensity beams, high density targets and large