Deviations from Tribimaximal Neutrino Mixing using a Model with $Δ(27)$ Symmetry

We present a model of neutrino mixing based on the flavour group $Δ(27)$ in order to account for the observation of a non-zero reactor mixing angle ($θ_{13}$). The model provides a common flavour structure for the charged-lepton and the neutrino sectors, giving their mass matrices a `circulant-plus-diagonal' form. Mass matrices of this form readily lead to mixing patterns with realistic deviations from tribimaximal mixing, including non-zero $θ_{13}$. With the parameters constrained by existing measurements, our model predicts an inverted neutrino mass hierarchy. We obtain two distinct sets of solutions in which the atmospheric mixing angle lies in the first and the second octants. The first (second) octant solution predicts the lightest neutrino mass, $m_3 \sim 29~\text{meV}$ ($m_3 \sim 65~\text{meV}$) and the $CP$ phase, $δ_{CP} \sim -\fracπ{4}$ ($δ_{CP} \sim \fracπ{2}$), offering the possibility of large observable $CP$ violating effects in future experiments.

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