Photodisintegration and electrodisintegration of 3He at threshold and pd radiative capture -: art. no. 064001

The present work reports results for (i) pd radiative capture observables at center-of-mass (c.m.) energies less than or equal to 2 MeV; (ii) contributions to the Gerasimov-Drell-Hearn (GDH) integral of He-3 in the threshold region; and (iii) longitudinal, transverse, and interference response functions, at excitation energies below the threshold for breakup into ppn, of interest in (3)<(He)over right arrow>((e) over right arrow,e') experiments. An exhaustive comparison of these results with available data from the TUNL and Wisconsin groups for pd capture, and from the Saskatoon group for threshold electrodisintegration of He-3, is carried out. The calculations are based on pair-correlated-hyperspherical-harmonics bound and continuum wave functions obtained from a realistic Hamiltonian consisting of the Argonne v(18) two-nucleon and Urbana IX three-nucleon interactions. The electromagnetic current operator includes one- and two-body components, leading terms of which are constructed from the Argonne v(18) interaction. The theoretical predictions obtained by including only one-body currents are in violent disagreement with data. These differences between theory and experiment are, to a large extent, removed when two-body currents are taken into account, although some rather large discrepancies remain in the c.m. energy range 0-100 keV, particularly for the pd differential cross section sigma(theta) and tensor analyzing power T-20(theta) at small angles, and contributions to the GDH integral. A rather detailed analysis indicates that these discrepancies have, in large part, a common origin, and can be traced back to an excess of E-1 strength obtained in the theoretical calculation as compared to that observed experimentally. It is suggested that this fact might have implications-for the nuclear interaction at very low energies. Finally, the validity of the long-wavelength approximation for electric dipole transitions is discussed.