Meson-Exchange Currents in Quasielastic Charged-Current Neutrino Reactions with Single-Nucleon Knockout

Abstract

The effect of meson-exchange currents on charged-current quasielastic neutrino scattering with single-nucleon emission is computed and analyzed within the relativistic Fermi gas model. This contribution arises primarily from the interference between one-body and two-body currents, where the two-body operator excites a 1p1h state in the presence of a second, spectator nucleon. The results obtained show a reduction of the vector, axial and vector-axial transverse response functions and, consequently, a decrease in the total neutrino cross section. In addition to a comparison with the non-relativistic limit, other models are also explored, such as the relativistic mean field model for nuclear matter and the superscaling analysis with relativistic effective mass, both of which yield qualitatively similar results.

Figures (19)

• Figure 1: Feynman diagrams for the electroweak MEC model used in this work.
• Figure 2: Exchange many-body diagrams of the MEC matrix elements contributing to the 1p1h excitation channel considered in this work.
• Figure 3: Interference response $R_{CC}^{AA}$ between the one-body axial current and the seagull current, for increasing values of the momentum transfer $q$, with $k_F = q/2$. In each panel, the non-relativistic results (red lines) are compared with the relativistic ones (black lines).
• Figure 4: Non-relativistic (dot-dashed lines) versus relativistic (solid lines) transverse interference response $R_T^{VV}$ between the 1b current and the seagull (black), pion-in-flight (red), and $\Delta$-excitation (blue) two-body currents, for increasing values of $q$ and with $k_F = q/2$.
• Figure 5: The same as Fig. \ref{['relneu7']} for the interference response $R_T^{AA}$ between the axial 1b and $\Delta$ currents