Measurement of Muon Neutrino Quasielastic Scattering on a Hydrocarbon Target at $E_{\nu }\sim 3.5\mathrm{GeV}$

We report a study of ${\nu }_{\mu }$ charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a ${\mu }^{-}$ and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, $d\sigma /d{Q}^2$, and study the low energy particle content of the final state. Deviations are found between the measured $d\sigma /d{Q}^2$ and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protons in the final state.

Figure 1

The measured recoil energy distribution in the data (solid circles) and the predicted composition of signal and background. Backgrounds from charged-current (CC) baryon resonance production (light gray), continuum or deep-inelastic scattering (DIS) (dark gray), and other sources (black), such as coherent pion production, are shown. The fraction of signal before requiring low recoil energy is 0.29.

Figure 2

The measured $Q_{\mathrm{QE}}^2$ distributions in the data and the simulation, before correcting for detector resolution and acceptance. The fraction of signal in this sample is 0.49, and 47% of signal events in our fiducial volume pass all selections.

Figure 3

Neutrino quasielastic cross section as a function of $Q_{\mathrm{QE}}^2$ compared with several different models of the interaction.

Figure 4

Ratio between the measured neutrino $d\sigma /d{Q}_{\mathrm{QE}}^2$ shape in $Q_{\mathrm{QE}}^2$ and several different models, where the denominator is the GENIE default quasielastic cross section.

Figure 5

Reconstructed vertex energy of events passing the selection criteria in the data (points with statistical errors) compared to the GENIE RFG model (shown with systematic errors) for $Q_{\mathrm{QE}}^2<0.2{\mathrm{GeV}}^2/c^2$ (top) and for $Q_{\mathrm{QE}}^2>0.2{\mathrm{GeV}}^2/c^2$ (bottom).