Impact of final state interactions on neutrino-nucleon pion production cross sections extracted from neutrino-deuteron reaction data

The current and near-future neutrino-oscillation experiments require significantly improved neutrinonucleus reaction models. Neutrino-nucleon pion production data play a crucial role to validate corresponding elementary amplitudes that go into such neutrino-nucleus models. Thus, the currently available data extracted from charged-current neutrino-deuteron reaction data (nu(mu)d -> mu(-)pi NN) must be corrected for nuclear effects such as the Fermi motion and final state interactions ( FSI). We study nu(mu)d -> mu(-)pi NN with a theoretical model including the impulse mechanism supplemented by FSI from NN and pi N rescatterings. An analysis of the spectator momentum distributions reveals that the FSI effects significantly reduce the spectra over the quasifree peak region and leads to a useful recipe to extract information of elementary nu(mu)d -> mu(-)pi NN processes using nu(mu)d -> mu(-)pi NN data, with the important FSI corrections taken into account. We provide nu(mu)d -> mu(-)pi N total cross sections by correcting the deuterium bubble chamber data for the FSI and Fermi motion. The results will bring a significant improvement on neutrino-nucleus reaction models for the near-future neutrino-oscillation experiments.