Identification of nuclear effects in neutrino-carbon interactions at low three-momentum transfer

TL;DR

This paper isolates and analyzes nuclear-medium effects in low three-momentum transfer neutrino-carbon interactions, revealing phenomena like nucleon correlation screening and multi-proton final states, crucial for improving neutrino oscillation models.

Contribution

It identifies and characterizes nuclear effects such as long-range correlations and multi-nucleon interactions in neutrino-carbon scattering at low momentum transfer, providing detailed cross sections for model refinement.

Findings

Observation of a small cross section at very low energy transfer consistent with nucleon correlation screening.

Detection of increased event rates and multi-proton final states between quasielastic and resonance regions.

Model improvements partially explain the data but require further refinement.

Abstract

Two different nuclear-medium effects are isolated using a low three-momentum transfer subsample of neutrino-carbon scattering data from the MINERvA neutrino experiment. The observed hadronic energy in charged-current $\nu_\mu$ interactions is combined with muon kinematics to permit separation of the quasielastic and $\Delta$(1232) resonance processes. First, we observe a small cross section at very low energy transfer that matches the expected screening effect of long-range nucleon correlations. Second, additions to the event rate in the kinematic region between the quasielastic and $\Delta$ resonance processes are needed to describe the data. The data in this kinematic region also has an enhanced population of multi-proton final states. Contributions predicted for scattering from a nucleon pair have both properties; the model tested in this analysis is a significant improvement but does not fully describe the data. We present the results as a double-differential cross section to enable further investigation of nuclear models. Improved description of the effects of the nuclear environment are required by current and future neutrino oscillation experiments.