A Poincare Invariant Model of Deuteron Elastic Structure Functions

Electrons from CEBAF at JLab have been used to probe the structure of the deuteron, the simplest nucleus in terms of a picture of nucleons in a bound state. Understanding the deuteron is one key in our understanding of more complex nuclei. Because the electron′s interaction with nucleons is through well understood electromagnetic forces, electron scattering plays a primary role in our investigation of the structure of the deuteron. Moreover, because the coupling constant alpha is small, the one-photon exchange process is the dominant component of the interaction and higher order diagrams are suppressed. Three independent observables can be extracted from elastic electron scattering from the deuteron, the Lorentz invariant structure functions A(Q2), B(Q2), and T_{20}(Q2), where Q2 is the square of the four- momentum transfer of the electron. Relativity should be considered in any such investigation when the momentum transfer and the rest energy of the constituent nucleon are comparable, as is the case at JLab energies. In our approach we use an exact Poincare invariant dynamical model in a two-nucleon Hilbert space plus a model of a covariant current operator, all within a light-front kinematics picture. The single-nucleon current is standard. The pair current has been constructed to be consistent with the realistic NN-interaction used to generate the deuteron wave function. The resulting deuteron structure functions agree with the experimental data, when the pair current contributions are included, to within the uncertainties of the emperical nucleon structure functions utilized. The magnetic moment is also consistent with the experimental value (to within 0.01%), while the deuteron quadrupole moment shows a discrepancy of about 4%.