Assessing the role of nuclear effects in the interpretation of the MiniBooNE low-energy anomaly

We study the impact of the effect of multinucleon interactions in the reconstruction of the neutrino energy on the fit of the MiniBooNE data in terms of neutrino oscillations. We obtain some improvement of the fit of the MiniBooNE low-energy excess in the framework of two-neutrino oscillations and a shift of the allowed region in the ${\sin }^{2}2\vartheta \text{−}\mathrm{\Delta }{m}^2$ plane toward smaller values of ${\sin }^{2}2\vartheta$ and larger values of $\mathrm{\Delta }{m}^2$. However, this effect is not enough to solve the problem of the appearance-disappearance tension in the global fit of short-baseline neutrino oscillation data.

Figure 1

Scatter plots which show the correlation between the true neutrino energy $E_{\nu }$ and the reconstructed neutrino energy $E_{\nu }^{\mathrm{rec}}$ in the original [96] MiniBooNE muon-to-electron neutrino and antineutrino Monte Carlo full transmutation events (upper plots) and in the events modified with the contribution of multinucleon interactions (lower plots). The color sequence (black, blue, magenta, green, yellow, and red) indicates an increasing density of points.

Figure 2

Scatter plots which shows the correlation between the true neutrino energy $E_{\nu }$ and the reconstructed neutrino energy $E_{\nu }^{\mathrm{rec}}$ separately for quasielastic, misidentified pion, and multinucleon events for neutrino (upper plots) and antineutrino (lower plots) scattering. The color sequence (black, blue, magenta, green, yellow, and red) indicates an increasing density of points.

Figure 3

Comparison between the background in the MiniBooNE data release (solid blue) and that obtained taking into account the multinucleon interactions (dashed red), with the respective systematic uncertainties. The left and right figures correspond, respectively, to the neutrino and antineutrino modes. The data are shown with statistical error bars.

Figure 4

Comparison of the theoretical excess over the background of ${\nu }_e$ and ${\overline{\nu }}_e$ events in MiniBooNE obtained with neutrino oscillations for some selected values of the oscillation parameters ${\sin }^{2}2\vartheta$ and $\mathrm{\Delta }{m}^2$ without (dotted lines) and with (solid lines) the multinucleon interactions.

Figure 5

MiniBooNE excess above the background with statistical (black) and $\mathrm{statistical}+\mathrm{systematic}$ (gray) error bars in the 11 energy bins of the MiniBooNE data release in neutrino (left) and antineutrino (right) mode without (top) and with (bottom) the multinucleon interactions. The histograms show the predicted excess for the best-fit values and for some other selected values of the oscillation parameters ${\sin }^{2}2\vartheta$ and $\mathrm{\Delta }{m}^2$ indicated by the crosses with corresponding color in Fig. 6.

Figure 6

Allowed regions in the ${\sin }^{2}2\vartheta \text{−}\mathrm{\Delta }{m}^2$ plane obtained in a two-neutrino mixing fit of MiniBooNE data without (MiniBooNE) and with ($\mathrm{MB}+\mathrm{multinucleon}$) the multinucleon interactions. The best-fit point is indicated by a blue asterisk. The other crosses indicate the values of ${\sin }^{2}2\vartheta$ and $\mathrm{\Delta }{m}^2$ considered in Fig. 5.

Figure 7

Allowed regions in the ${\sin }^{2}2{\vartheta }_{e\mu }\text{−}\mathrm{\Delta }{m}_{41}^2$ plane obtained in the $3+1$ global fit of short-baseline neutrino oscillation data, taking into account the MiniBooNE data without (left) and with (right) the multinucleon interactions. In both figures, the region inside the blue curve is allowed at $3\sigma$ by ${\stackrel{(-)}{\nu }}_{\mu }\to {\stackrel{(-)}{\nu }}_e$ appearance data, with the best fit indicated by the blue cross; the region on the right of the red curve is excluded at $3\sigma$ by ${\stackrel{(-)}{\nu }}_e$ and ${\stackrel{(-)}{\nu }}_{\mu }$ disappearance data; and the green-yellow shadowed regions are allowed at $1,2,3\sigma$ by the global fit of all short-baseline neutrino oscillation data.