Atmospheric Mass-Squared Splitting at Sub-Percent Precision as a $CPT$ Symmetry Probe

Abstract

In this paper, we present an improved test of $CPT$ symmetry in the neutrino sector by analyzing the atmospheric mass-squared splittings, $\Delta m_{31}^2$ and $\Delta {\overline{m}}_{31}^2$, using on-going JUNO and future DUNE and Hyper-Kamiokande experiments. Our study focuses on the discrepancy ${\delta }_{\nu \overline{\nu }}(\Delta m_{31}^2)=\Delta m_{31}^2-\Delta {\overline{m}}_{31}^2$, achieving unprecedented precision by exploiting the high statistics and reduced systematic uncertainties of these facilities. The combined analysis yields a sensitivity to $CPT$ violation at the level of $2\times 10^{-5}{\text{eV}}^2$ at $3\sigma$ confidence level, representing a $60\%$ improvement over the joint T2K-NO$\nu$A-JUNO analysis. These results highlight the crucial role of multi-experiment synergies in testing fundamental symmetries of nature.

Comments: 7 pages, 6 figures