Effect of systematics in the T2HK, T2HKK, and DUNE experiments

T2HK and T2HKK are the proposed extensions of the T2K experiments in Japan and DUNE is the future long-baseline program of Fermilab. These three experiments will use extremely high beam power and large detector volumes to observe neutrino oscillation. Because of the large statistics, these experiments will be highly sensitive to systematics. Thus a small change in the systematics can cause a significant change in their sensitivities. To understand this, we do a comparative study of T2HK, T2HKK, and DUNE with respect to their systematic errors. Specifically we study the effect of the systematics in the determination of neutrino mass hierarchy, octant of the mixing angle ${\theta }_{23}$, and ${\delta }_{CP}$ in the standard three-flavor scenario, and we also analyze the role of systematic uncertainties in constraining the parameters of the nonstandard interactions in neutrino propagation. Taking the overall systematics for signal and background normalization, we quantify how the sensitivities of these experiments change if the systematics are varied from 1% to 7%.

Figure 1

Fraction of the true ${\delta }_{CP}$ for which $CP$ violation can be discovered for $5\sigma$ vs systematics. In all the panels the true ${\theta }_{23}$ is 45°. The left panel is for NH and the right panel is for IH.

Figure 2

Hierarchy sensitivity vs systematics. In all the panels the true value of ${\theta }_{23}$ is 45°. The true ${\delta }_{CP}$ is $-90°$ for the left column and $+90°$ for the right column. The upper row corresponds to the true NH and the lower row corresponds to the true IH.

Figure 3

Octant sensitivity vs systematics. The upper row corresponds to NH and the lower row corresponds to IH. Sensitivities are given for two values of ${\theta }_{23}$, i.e., 42° and 48° and for ${\delta }_{CP}=-90°$.

Figure 4

Sensitivity for NSI parameters for four values of the systematic errors. The left column is for NH and the right column is for IH. The thin solid diagonal straight line stands for the bound $|\tan \beta |=|{\epsilon }_{e\tau }/(1+{\epsilon }_{ee})|\lesssim 0.8$ [72] at $3\sigma$ from the current atmospheric data by Super-Kamiokande. The first three rows correspond to the 2.5°, 2.0°, and 1.5° off-axis configurations for T2HKK, respectively. The fourth row is for DUNE.

Figure 5

Sensitivity to the $CP$ phases for four values of the systematic errors. The left column is for NH and the right column is for IH. The first three rows correspond to the 2.5°, 2.0°, and 1.5° off-axis configurations for T2HKK, respectively. The fourth row is for DUNE.