Neutrino cross sections and weak structure functions for low momentum transfers

Deep-inelastic scattering of neutrinos and antineutrinos on nucleon and nuclear targets probes the partonic content of the targets. As the momentum transfer Q decreases, the parton model-based approach is not applicable. We adapt the low-Q electromagnetic structure functions by Capella et al. to neutrino scattering by matching to next-to-leading order weak structure functions based on the parton model at Q=2 GeV. For charged-current scattering with final state invariant masses larger than 1.4-2.0 GeV, we show the impact on the cross section of a PCAC structure function correction. We compare our cross section results with the those using the Bodek-Yang prescription and with the recent Candido et al. low-Q weak structure functions modeled by a machine-learning parameterization of neutrino and antineutrino scattering data. We find discrepancies between the cross sections evaluated at low-Q using our approach and using the Candido et al. low-Q structure functions for isoscalar nucleon targets, however, there is good agreement for heavier targets. We discuss the relevance of the low-Q weak structure functions to experiments at a future Forward Physics Facility at the Large Hadron Collider.