Abstract
Nuclear electromagnetic currents are derived in time-ordered perturbation theory within an effective-field-theory framework including explicit nucleons, Δ isobars, and pions up to one loop, or next-to-next-to-next-to-leading order (LO). The currents obtained at next-to-next-to-leading order (LO), i.e., ignoring loop corrections, are used in a study of neutron radiative captures on protons and deuterons at thermal energies, and of and 3 nuclei magnetic moments. The wave functions for are derived from solutions of the Schrödinger equation with the Argonne (AV18) or CD-Bonn (CDB) potentials, while those for are obtained with the hyperspherical-harmonics-expansion method from a realistic Hamiltonian including, in addition to the AV18 or CDB two-nucleon, a three-nucleon potential. With the strengths of the Δ-excitation currents occurring at LO determined to reproduce the cross section and isovector combination of the trinucleon magnetic moments, we find that the cross section and photon circular polarization parameter, measured in and processes, are underpredicted by theory; for example, the cross section is underpredicted by 11–38% as the cutoff is increased from 500 to 800 MeV. A complete analysis of the results, in particular their large cutoff dependence, is presented.
6 More- Received 10 October 2008
DOI:https://doi.org/10.1103/PhysRevC.78.064002
©2008 American Physical Society