Constraining Sterile Neutrinos Using Reactor Neutrino Experiments

TL;DR

This paper uses reactor neutrino experiment data, especially from Daya Bay and JUNO, to constrain sterile neutrino models, providing upper bounds on active-sterile mixing and assessing impacts on standard neutrino parameters.

Contribution

It offers new bounds on active-sterile mixing angles from reactor experiments and evaluates their impact on standard neutrino oscillation measurements.

Findings

Daya Bay constrains $ heta_{14}$ to less than 0.06 at 3$\sigma$

JUNO can improve bounds to $ heta_{14} < 0.016$ over six years

Sterile neutrinos generally do not significantly affect standard oscillation parameter measurements

Abstract

Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\sin^2 2 \theta_{14} \lesssim 0.06$ at 3$\sigma$ confidence level for the mass-squared difference $\Delta m^2_{41}$ in the range $(10^{-3},10^{-1}) \, {\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\sin^22\theta_{14} \lesssim 0.016$, although in the smaller mass range $ \Delta m^2_{41} \in (10^{-4} ,10^{-3}) \, {\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $\theta_{13}$ and $\Delta m^2_{31}$ (at Daya Bay and JUNO), $\theta_{12}$ and $\Delta m^2_{21}$ (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where $\Delta m^2_{41}\sim \Delta m^2_{31}$, sterile states do not affect these measurements substantially.