Enhancing the sensitivity to neutrino oscillation parameters using synergy between T2K, NOνA and JUNO

A

bstract

We study the impact of combining the present NO ν A and T2K data with simulated data from the JUNO experiment on the determination of the leptonic CP phase and the neutrino mass hierarchy. The current NO ν A data exhibit a hierarchy- δ _CP degeneracy, admitting both normal hierarchy (NH) with δ _CP ∈ [0 , 180 ° ], and inverted hierarchy (IH) with δ _CP ∈ [180 ° , 360 ° ] solutions at comparable significance, while T2K prefers δ _CP ≃ 270 ° for both hierarchies, leading to a 2 σ tension between the two experiments for normal hierarchy. Using detailed GLoBES simulations, we show that future JUNO data with excellent hierarchy sensitivity, can lift the hierarchy- δ _CP degeneracy in NO ν A and strengthen the hierarchy reach of T2K in spite of having no δ _CP sensitivity. Allowing the hierarchy to be a free parameter in the fit, if the true ordering is IH, JUNO aligns the NO ν A and T2K allowed regions and resolves their present tension; if NH is true, the tension continues to persist. We also show that JUNO’s precise measurement of |∆ ₃₁ | leads to improved constraints on sin ² θ ₂₃ and δ _CP for normal mass hierarchy in NOνA even though JUNO itself is insensitive to these parameters . Finally, updated solar-parameter measurements from JUNO’s first data release further enhance the combined precision. Our results demonstrate that JUNO plays a crucial synergistic role in the global neutrino-oscillation programme, enabling a more robust determination of the mass ordering and improving the sensitivity to the CP phase when combined with long-baseline data.