Neutrino mass ordering in JUNO at risk from scalar NSI induced resonance

Abstract

The determination of neutrino mass ordering (NMO) is the primary goal of the currently running JUNO reactor experiment. We show that the measurement of NMO at JUNO may severely deteriorate in the presence of non-standard neutrino interactions mediated by a beyond standard model scalar (SNSI). Taking inverted ordering and the lightest neutrino mass at $m_l=0.01$ eV, the NMO sensitivity falls below $2σ$ for SNSI parameter values in the range $η_{ee}< -7.1\times 10^{-3}$ and $η_{ee} > 3.3\times 10^{-3}$. More importantly, for $η_{ee} \gtrsim 5.7\times 10^{-3}$ the NMO sensitivity in JUNO is completely lost. We show that this is due to the presence of a hitherto unrecognized resonant enhancement of the mixing angle $θ_{12}$, which gives rise to a mass ordering degeneracy.

Figures (4)

• Figure 1: Neutrino mass ordering sensitivity of JUNO, when $\eta_{ee}$ is present in nature but not in the fit. Data is simulated with assumed inverted ordering (IO) and various values of the SNSI parameter $\eta_{ee}$. The lightest neutrino mass is assumed to be $m_l=0.01$ eV in all cases.
• Figure 2: Probability difference between simulated data and best fit assuming NO (top-panel) and IO (bottom-panel), as function of neutrino energy. See the text for details.
• Figure 3: Average integrated probability difference in the $m_l-\eta_{ee}$ plane. The right-panel shows $\overline{|\Delta P_{NO}|}=\overline{|P_{\rm{IO}}^{\eta_{ee}}-P_{\rm{NO}}^{\rm{bf}}|}$ and the left-panel shows $\overline{|\Delta P_{IO}|}=\overline{|P_{\rm{IO}}^{\eta_{ee}}-P_{\rm{IO}}^{\rm{bf}}|}$. The best fit is restricted to $\theta_{12}^{\rm{bf}}<\pi/4$.
• Figure 4: Effective oscillation parameters as functions of $\eta_{ee}$.