The neutrino mass scale and the mixing angle θ₁₃ for quasi-degenerate Majorana neutrinos

Considering a general mass matrix for quasi-degenerate neutrinos and treating the experimentally known oscillation parameters as inputs, we study the correlation between the degenerate mass scale $(m)$ and the mixing angle $\theta_{13}$. We find that, corresponding to different values of $m$, there exist upper bounds on $\theta_{13}$, so that a precise determination of the latter in future may put upper limit on the former, and vice versa. One can also find a possible correlation between $m$ and lower bound of $\theta_{13}$, depending on the relative strength of the unperturbed degenerate mass matrix and the perturbation. The possible constraints on the parameters of few models of quasi-degenerate neutrinos are briefly discussed.