Relevance of Two Boson Exchange Effect in Quasi-Elastic Charged Current Neutrino-Nucleon Interaction

Two boson exchange (TBE) correction to the cross section for the quasi-elastic charged current $\nu n$ and $\bar{\nu} p$ scattering is evaluated. The TBE is given by $W\gamma$ box diagrams. The calculations are performed for 1 GeV neutrinos. The averaged TBE correction is of the order of $2\div4 %$ (with respect to Born contribution) in the case of $\nu_e$ and $\bar{\nu}_e$ and $1\div2 %$ in the case of $\nu_\mu$ and $\bar{\nu}_\mu$. The impact of the TBE effect on the systematic discrepancy between the $\nu_e$ and $\nu_\mu$ cross sections is discussed.