Selected electromagnetic processes in three-nucleon systems

The central dynamical ingredient for electromagnetic processes in three-nuc leon systems is the nuclear current operator. It consists of a single nucle on part and more than one-nucleon parts. Due to the spin structure of the H e-3 wave function, polarized He-3 targets are used as effective neutron tar gets with the aim to extract the magnetic (G(M)(n)) and electric (G(E)(n)) neutron form factors at certain Q(2) values. In this talk we present an analysis of two recent experiments [1,2] on the processes He-3((e) over right arrow, e ') and He-3((e) over right arrow, e 'n). This theoretical analysis is based on E'addeev solutions for the three -nucleon continuum and the three-nucleon bound state belonging to the same three-nucleon Hamiltonian [3-5]. We use realistic, nucleon-nucleon forces a nd incorporate mesonic exchange currents [6]. The analysis [7] of the exclu sive experiment by consistent Faddeev solutions for the three-nucleon conti nuum and 3He has not been done before to the best of our knowledge. Extract ed values for G(M)(n) in case of the inclusive process and Gn, in case of t he exclusive process agree well with the ones extracted from processes on t he deuteron. Within the same framework we investigate the proton-deuteron radiative capt ure process at various energies. The application of the Siegert theorem is compared to the explicit use of pi- and rho -like exchange currents connect ed to the Argonne nucleon-nucleon potentials. Good agreement with cross sec tions and spin observables is obtained. We demonstrate that the different m odern nucleon-nucleon forces taken together with the Siegert theorem give e ssentially the same predictions.