Physics Reach of DUNE with a Light Sterile Neutrino

TL;DR

This paper evaluates how a light sterile neutrino affects DUNE's ability to determine neutrino mass hierarchy and CP violation, showing potential reductions in sensitivity and the ability to reconstruct CP phases.

Contribution

It provides a detailed analysis of the impact of a 3+1 sterile neutrino scheme on DUNE's physics reach, including sensitivity to mass hierarchy and CP violation.

Findings

Mass hierarchy sensitivity remains above 5σ if mixing angles are small.

CP violation sensitivity decreases in the presence of sterile neutrinos.

DUNE can probe CP violation due to the new phase δ_{34} if θ_{34} is large.

Abstract

We investigate the implications of one light eV scale sterile neutrino on the physics potential of the proposed long-baseline experiment DUNE. If the future short-baseline experiments confirm the existence of sterile neutrinos, then it can affect the mass hierarchy (MH) and CP-violation (CPV) searches at DUNE. The MH sensitivity still remains above 5$\sigma$ if the three new mixing angles ($\theta_{14}, \theta_{24}, \theta_{34}$) are all close to $\theta_{13}$. In contrast, it can decrease to 4$\sigma$ if the least constrained mixing angle $\theta_{34}$ is close to its upper limit $\sim 30^0$. We also assess the sensitivity to the CPV induced both by the standard CP-phase $\delta_{13} \equiv \delta$, and the new CP-phases $\delta_{14}$ and $\delta_{34}$. In the 3+1 scheme, the discovery potential of CPV induced by $\delta_{13}$ gets deteriorated compared to the 3$\nu$ case. In particular, the maximal sensitivity (reached around $\delta_{13}$ $\sim$ $\pm$ $90^0$) decreases from $5\sigma$ to $4\sigma$ if all the three new mixing angles are close to $\theta_{13}$. It can further diminish to almost $3\sigma$ if $\theta_{34}$ is large ($\sim 30^0$). The sensitivity to the CPV due to $\delta_{14}$ can reach 3$\sigma$ for an appreciable fraction of its true values. Interestingly, $\theta_{34}$ and its associated phase $\delta_{34}$ can influence both the $\nu_e$ appearance and $\nu_\mu$ disappearance channels via matter effects, which in DUNE are pronounced. Hence, DUNE can also probe CPV induced by $\delta_{34}$ provided $\theta_{34}$ is large. We also reconstruct the two phases $\delta_{13}$ and $\delta_{14}$. The typical 1$\sigma$ uncertainty on $\delta_{13}$ ($\delta_{14}$) is $\sim20^0$ ($30^0$) if $\theta_{34} =0$. The reconstruction of $\delta_{14}$ (but not that of $\delta_{13}$) degrades if $\theta_{34}$ is large.