Neutrino cuboid for normal mass ordering and tribimaximal flavor mixing

Abstract

Given the latest JUNO implication for normal neutrino mass ordering, we parametrize three neutrino masses in a flavor cuboid: $m^{}_1 = m^{}_0 \sinξ$, $m^{}_2 = m^{}_0 \cosξ\sinζ$ and $m^{}_3 = m^{}_0 \cosξ\cosζ$. We find that this cuboid is able to accommodate both neutrino mass degeneracy and tribimaximal flavor mixing in its cubic limit with $ξ^{}_* = \arctan\left(1/\sqrt{2}\right) \simeq 35.26^\circ$ and $ζ^{}_* = 45^\circ$. Assuming $θ^{}_{12} = ξ$ and $θ^{}_{23} = ζ$ for the two large angles of neutrino oscillations and expanding them around $ξ^{}_*$ and $ζ^{}_*$, we propose a viable ansatz which predicts a normal but nearly degenerate neutrino mass spectrum and a nearly tribimaximal neutrino mixing pattern. Testing the achieved correlation among $ξ^{}_* - θ^{}_{12}$, $ζ^{}_* - θ^{}_{23}$ and $Δm^2_{21}/Δm^2_{31}$ will provide a smoking gun for the validity of this ansatz.