arXiv:nucl-th/0304084·v2·Nuclear Theory
The 2p-2h electromagnetic response in the quasielastic peak and beyond
A. De Pace (1) · M. Nardi (1) · W. M. Alberico (1) · T. W. Donnelly (2) · A. Molinari (1) ((1) INFN and Dipartimento di Fisica Teorica, Torino, Italy;(2) Center for Theoretical Physics, MIT, Cambridge, USA)
Abstract
The contribution to the nuclear transverse response function R_T arising from two particle-two hole (2p-2h) states excited through the action of electromagnetic meson exchange currents (MEC) is computed in a fully relativistic framework. The MEC considered are those carried by the pion and by Delta degrees of freedom, the latter being viewed as a virtual nucleonic resonance. The calculation is performed in the relativistic Fermi gas model in which Lorentz covariance can be maintained. All 2p-2h many-body diagrams containing two pionic lines that contribute to R_T are taken into account and the relative impact of the various components of the MEC on R_T is addressed. The non-relativistic limit of the MEC contributions is also discussed and compared with the relativistic results to explore the role played by relativity in obtaining the 2p-2h nuclear response.
Comments: 27 pages, 12 figures, revtex4; minor modifications in the discussion of the results, references added