Relating small neutrino masses and mixing

Experiments on neutrino oscillations have uncovered several small parameters, ${\theta }_{13}$ being a prominent one. Others are the solar mass splitting {\em vis-`{a}-vis} the atmospheric one and the deviation of ${\theta }_{23}$ from maximal mixing. In this talk we elaborate on a neutrino mass model based on the see-saw mechanism in which the mixing angles to start with are either vanishing (${\theta }_{13}$ and ${\theta }_{12}$) or $\pi \mathrm{/}4$ (${\theta }_{23}$). The atmospheric mass splitting is taken as a part of this initial structure but the solar splitting is absent. A perturbative contribution, originating from a Type-I see-saw, results in non-zero values of ${\theta }_{13}$, ${\theta }_{12}$, $\Delta m^2_{solar}$,andshifts$\theta_{23}$slightlyfrom$\pi/4$, interrelating them all. The model incorporates CP-violation, the phase $\delta$ being close to 3$\pi$/2 for (a) quasi-degeneracy or (b) inverted mass ordering. It will be put to test as the neutrino parameters get better determined.