Pionic correlations and meson-exchange currents in two-particle emission induced by electron scattering

TL;DR

This paper calculates two-particle emission responses in electron scattering using a relativistic Fermi gas model, focusing on pionic correlations and meson-exchange currents, and finds they are similarly significant.

Contribution

It provides a comprehensive relativistic calculation of two-particle emission, including all relevant one-pion exchange diagrams and regularization of divergences.

Findings

Pionic correlations are comparable to meson-exchange currents in magnitude.

Regularization of divergences is achieved by modifying the nucleon propagator.

Both effects are essential for accurate response function calculations.

Abstract

Two-particle two-hole contributions to electromagnetic response functions are computed in a fully relativistic Fermi gas model. All one-pion exchange diagrams that contribute to the scattering amplitude in perturbation theory are considered, including terms for pionic correlations and meson-exchange currents (MEC). The pionic correlation terms diverge in an infinite system and thus are regularized by modification of the nucleon propagator in the medium to take into account the finite size of the nucleus. The pionic correlation contributions are found to be of the same order of magnitude as the MEC.