Neutrino masses and flavor mixing in the Extended Double Seesaw Model with two texture zeros

We study the light neutrino mass matrix in the Extended Double Seesaw Model (EDSM), and as a result we get its general form. Also we demonstrate that conventional type-I and double seesaw mechanisms can be regarded as two special cases. We analyze the structure of the 9×9 neutrino mass matrix in this scenario, and surprisingly we find that EDSM will degenerate to a conventional type-I seesaw mechanism when \(M_{\mathrm{R}}= M_{\mathrm{S}}M_{\mu}^{-1}M_{\mathrm{S}}^{T}\) holds exactly. Considering two simple ansätze in two texture zeros for its 3×3 submatrices, we calculate the neutrino masses and flavor mixing angles, in which the θ ₁₃ is a nonzero large angle.