Light Front Field Theory Calculation of Deuteron Properties

Light Front Field Theory Calculation of Deuteron Properties by Jason Randolph Cooke Chair of Supervisory Committee:Professor Gerald A. MillerDepartment of Physics Light front dynamics is a promising approach for solving bound state problems innuclear physics. It is also ideal for calculating the deuteron form factors at highmomentum transfers. However, in light-front dynamics rotational invariance is notmanifest, which results in a splitting in the binding energies of states with differentmagnetic quantum numbers and a breaking of the angular condition for the matrixelements of the deuteron current operator. The objective of this work is to inves-tigate the symptoms of broken rotational invariance for deuterons calculated usingone-meson-exchange (OME) and two-meson-exchange (TME) potentials for variousmodels.We first consider the Wick-Cutkosky model. The binding energies of states withdifferent m values are split when calculated with the OME potential, but this splittingis reduced for all states when the TME potential is included. In addition, we findthat appropriate OME+TME potentials give almost identical results to the ladderand crossed ladder Bethe-Salpeter equation.Next, we derive light-front nucleon-nucleon OME and TME potentials from aneffective nuclear Lagrangian. We consider first the potentials generated by the exchange of pions only. There is a large splitting in the binding energies between them = 0 and m = 1 deuteron states when the one-pion-exchange (OPE) potentialis used. Including the chiral two-pion-exchange (TPE) potential in the calculationreduces this splitting. We then proceed to use the potentials generated by all themesons, and find that the deuteron mass splittings are smaller for both the OME andOME+TME potentials than in the pion-only model.The deuteron wave functions are used to calculate the electromagnetic and axialcurrent matrix elements and form factors. The matrix elements of the electromag-netic current operator have better transformation properties under rotations whenwe use the OME potential instead of the OME+TME potential to calculate the wavefunctions. The axial current matrix elements have about the same transformationproperties regardless of whether the OME or OME+TME potential is used. Finally,at momentum transfers greater than about 2 GeV, the breaking of rotational invari-ance causes less uncertainty in the A and B form factors than do the uncertainties inthe nucleon form factors.