Two-particle two-hole excitations in semi-inclusive neutrino-nucleus scattering

A calculation of the two-particle two-hole contribution to the semi-inclusive $({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}}N)$ cross section on carbon is performed in the framework of the relativistic Fermi gas model. The process is driven by meson-exchange currents encompassing all contributions involving the exchange of a single pion and the excitation of a $\mathrm{\ensuremath{\Delta}}$ resonance. The calculation is validated against the inclusive $({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}})$ response functions already existing in the literature, and then extended for the first time to the semi-inclusive channel. Results are presented both at fixed neutrino energy and folded with the T2K neutrino flux.