Measurement of the Inclusive Electron Neutrino Charged Current Cross Section on Carbon with the T2K Near Detector

The T2K off-axis near detector ND280 is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies $\sim 1\mathrm{GeV}$ as a function of electron momentum, electron scattering angle, and four-momentum transfer of the interaction. The total flux-averaged ${\nu }_e$ charged current cross section on carbon is measured to be $⟨\sigma {⟩}_{\varphi }=1.11\pm 0.10(\text{stat})\pm 0.18(\text{syst})\times 10^{-38}{\mathrm{cm}}^2/\text{nucleon}$. The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is $1.23\times 10^{-38}{\mathrm{cm}}^2/\text{nucleon}$ and the GENIE prediction is $1.08\times 10^{-38}{\mathrm{cm}}^2/\text{nucleon}$. The total ${\nu }_e$ charged current cross-section result is also in agreement with data from the Gargamelle experiment.

Figure 1

Reconstructed $p_e$ (top), $\cos ({\theta }_e)$ (middle), and $Q_{QE}^2$ (bottom) distributions of ${\nu }_e$ event candidates. The NEUT MC prediction is separated into the ${\nu }_e$ CC interaction signals from CCQE and CCnonQE interactions, background from $\gamma \to e^{+}{e}^{-}$ conversions, background from ${\mu }^{-}$ tracks and all other backgrounds.

Figure 2

Unfolded ${\nu }_e$ CC inclusive differential cross sections as a function of $p_e$ (top), $\cos ({\theta }_e)$ (middle), and $Q_{QE}^2$ (bottom). The inner (outer) error bars show the statistical (total) uncertainty on the data. The dashed (solid) line shows the NEUT (GENIE) prediction. Overflow (underflow) bins are indicated by $>$ ($<$) labels, and are normalized to the width shown.

Figure 3

Total ${\nu }_e$ CC inclusive cross section when unfolding through $Q_{QE}^2$. The T2K data point is placed at the ${\nu }_e$ flux mean energy. The vertical error represents the total uncertainty, and the horizontal bar represents 68% of the flux each side of the mean. The T2K flux distribution is shown in gray. The NEUT and GENIE predictions are the total ${\nu }_e$ CC inclusive predictions as a function of neutrino energy. The NEUT and GENIE averages are the flux-averaged predictions. Gargamelle ${\nu }_e$ and T2K ${\nu }_{\mu }$ data are taken from Ref. [9] and Ref. [6], respectively.

Figure 4

Unfolded ${\nu }_e$ CC inclusive differential cross section as a function of $Q_{QE}^2$, when only electrons with $p_e>550\mathrm{MeV}$ and $\cos ({\theta }_e)>0.72$ are considered. The inner (outer) error bars show the statistical (total) uncertainty on the data. The dashed (solid) line shows the NEUT (GENIE) prediction. The overflow bin is indicated by $>$, and is normalized to the width shown.