182.1 Introduction Neutrinos exist in three flavours v_e, v_μ and v_τ and mix with each other as they propagate which is known as neutrino oscillation. Neutrino oscillation occurs since neutrinos are massive and the flavour eigenstates are mixture of mass eigenstates. The mixing is described by PMNS matrix [1], which can be parametrized in terms of three mixing angles (θ_(12), θ_(13) and θ_(23)) and three phases (one Dirac phase δ_(CP) and two Majorana phases). Neutrino oscillation experiments explore mass-square differences (?m~2_(ii)= m~2_i - m~2_i), mixing angles (θ_(ij)) and Dirac phase (δCP). Results from various neutrino oscillation experiments show that cobimaximal mixing ({formula} ) is a good approximation to lepton mixing. Here we consider a model based on A4 symmetry which gives cobimaximal mixing in neutrino sector and Z_2 × Z_2 invariant perturbation in charged lepton sector to accommodate the results from recent neutrino oscillation experiments. The details of model and perturbation is given in Sects. 182.2 and 182.3 respectively and we conclude our discussion in Sect. 182.4.
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