Stringent constraint on CPT violation with the synergy of T2K-II, NO$\nu$A extension, and JUNO

TL;DR

This paper evaluates the sensitivity of upcoming neutrino experiments T2K-II, NOvA extension, and JUNO to test CPT symmetry by measuring differences in neutrino and antineutrino oscillation parameters, setting stringent limits on CPT violation.

Contribution

It provides the first empirical sensitivity analysis of combined T2K-II, NOvA, and JUNO data for CPT violation in neutrino oscillations, establishing new potential limits.

Findings

Limits on CPT violation: $| ext{difference in } ext{mass-squared differences}| < 5.3 imes 10^{-3} ext{eV}^2$

Potential to exclude CPT conservation at 4$\sigma$ if current differences persist

Sensitivity depends on true values of mixing angles, especially $ heta_{23}$

Abstract

Neutrino oscillation experiments have measured precisely the mass-squared differences of three neutrino mass eigenstates, and three leptonic mixing angles by utilizing both neutrino and anti-neutrino oscillations. The possible CPT violation may manifest itself in the difference of neutrino and anti-neutrino oscillation parameters, making these experiments promising tools for testing CPT invariance. We investigate empirically the sensitivity of the CPT test via the difference in mass-squared splittings ($\Delta m^2_{31} - \Delta \overline{m}^2_{31}$) and in leptonic mixing angles ($\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}$) with the synergy of T2K-II, NO$\nu$A extension, and JUNO experiments. If the CPT symmetry is found to be conserved, the joint analysis of the three experiments will be able to establish limits of $|\Delta m^2_{31} - \Delta \overline{m}^2_{31}|$ < $5.3\times 10^{-3} \text{eV}^2$ and $|\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}|$ < $0.10$ at 3$\sigma$ C. L. on the possible CPT violation. We find that with ($\Delta m^2_{31} - \Delta \overline{m}^2_{31}$), the dependence of the statistical significance on the relevant parameters to exclude the CPT conservation is marginal, and that, if the difference in the best-fit values of $\Delta m^2_{31}$ and $\Delta \overline{m}^2_{31}$ measured by MINOS(+) and NO$\nu$A persists as the true, the combined analysis will rule out the CPT conservation at 4$\sigma$ C. L.. With the ($\sin^2\theta_{23} - \sin^2\overline{\theta}_{23}$), the statistical significance to exclude CPT invariance depends strongly on the true value of $\theta_{23}(\overline{\theta}_{23})$. In case of maximal mixing of $\theta_{23}$, the CPT conservation will be excluded at 3$\sigma$ C. L. or more if the difference in the best-fit values of $\theta_{23}$ and $\overline{\theta}_{23}$ remains as the true.