Invisible neutrino decay in the light of NOvA and T2K data

Abstract

We probe for evidence of invisible neutrino decay in the latest NOvA and T2K data. It is seen that both NOvA and T2K data sets are better fitted when one allows for invisible neutrino decay. We consider a scenario where only the third neutrino mass eigenstate $\nu_3$ is unstable and decays into invisible components. The best-fit value for the $\nu_3$ lifetime is obtained as $\tau_{3}/m_{3} = 3.16\times 10^{-12}$ s/eV from the analysis of the NOvA neutrino data and $\tau_{3}/m_{3} = 1.0\times 10^{-11}$ s/eV from the analysis of the T2K neutrino and anti-neutrino data. The combined analysis of NOvA and T2K gives $\tau_{3}/m_{3} = 5.01\times 10^{-12}$ s/eV as the best-fit lifetime. However, the statistical significance for this preference is weak with the no-decay hypothesis still allowed at close to 1.5$\sigma$ C.L. from the combined data sets, while the two experiment individually are consistent with no-decay even at the 1$\sigma$ C.L. At 3$\sigma$ C.L., the NOvA and T2K data give a lower limit on the neutrino lifetime of $\tau_{3}/m_{3}$ is $\tau_{3}/m_{3} \geq 7.22 \times 10^{-13}$ s/eV and $\tau_{3}/m_{3} \geq 1.41 \times 10^{-12}$ s/eV, respectively, while NOvA and T2K combined constrain $\tau_{3}/m_{3} \geq 1.50 \times 10^{-12}$ s/eV. We also show that in presence of decay the best-fit value in the $\sin^{2}\theta_{23}$ vs $\Delta m^{2}_{32}$ plane changes significantly and the allowed regions increase significantly towards higher $\sin^{2}\theta_{23}$.