The Daya Bay Collaboration [1] has recently proclaimed discovery of nonzero reactor angle, θ 13 , sin 2 2θ 13 =0.092±0.016(stat)±0.005(syst), at 5.2σ which is in conformity with the earlier observations of T2K[2], MINOS[3] and DOU-BLE CHOOZ[4] last year. The discovery has immense implication for exploring CP -violation in the leptonic sector. In the present work, we examine CPviolation in Majorana neutrino mass matrix, in the basis where charged lepton mass matrix is diagonal, in which the ratio of elements are equal, also, termed as Strong Scaling Ansätz (SSA). This Ansätz has been known to explain the vanishing of θ 13 and predict inverted hierarchy (IH) for the neutrino masses. However, to generate a non-zero value of θ 13 consistent with Daya Bay result one has to deviate from SSA. This deviation will have important implications for CP -violation in the leptonic sector and is one of the issues addressed in the present work. CP is maximally violated because, for central value of θ 13 obtained from Daya Bay experiment, Dirac-type phase |δ| ≈ π 2 , 3π 2 which corresponds to |J CP | ≈ 0.03. We have, also, studied imperative implications for Majorana-type phases α, β and effective neutrino mass, M ee . The Majoranatype phases α, β are found to be sharply constrained. * s 7verma@yahoo.co.in

In the present work, we have considered minimal unitarity violation(MUV) scheme, to obtain the general expression for ν µ → ν τ oscillation probability, in vacuum. For this channel, we have investigated the sensitivities to nonunitary parameters |ρ µτ | and ω µτ with short baseline(SBL) experiments for normal as well as inverted hierarchical neutrino masses. We also check how the sensitivity to non-unitary parameters get modified for θ 23 above and below maximality. We find that the 3σ sensitivity towards |ρ µτ | is maximum for nonunitary phase ω µτ = 0, whereas it is minimum for ω µτ = ±π in case of normal hierarchy(NH). However, the sensitivity is minimum at ω µτ = 0 and maximum for ω µτ = ±π for inverted hierarchy(IH). We observe that for unitary CP phase δ = 0 and δ = π/2, the sensitivity to measure non-unitarity remains same in both the cases. We, also, explore wide range of L/E to forecast, in principle, the possibilities to observe CP -violation due to unitary(δ) and non-unitary(ω µτ ) phases. We find that the both phases can be disentangled, in principle, from each other, for the L/E range less than 200 km/GeV for ν µ → ν τ channel.

We investigate neutrino mass model based on A4 discrete flavor symmetry in type-I+II seesaw framework. The model has imperative predictions for neutrino masses, mixing and CP violation testable in the current and upcoming neutrino oscillation experiments. The important predictions of the model are: normal hierarchy for neutrino masses, a higher octant for atmospheric angle (θ23 > 45 o ) and near-maximal Dirac-type CP phase (δ ≈ π/2 or 3π/2) at 3σ C. L.. These predictions are in consonance with the latest global-fit and results from Super-Kamiokande(SK), NOνA and T2K. Also, one of the important feature of the model is the existence of a lower bound on effective Majorana mass, |Mee| ≥ 0.047eV(at 3σ) which corresponds to the lower part of the degenerate spectrum and is within the sensitivity reach of the neutrinoless double beta decay(0νββ) experiments.

The future long baseline experiments such as DUNE and T2HKK have promising prospects to determine the neutrino mass hierarchy and measuring standard CP phase δ. However, presence of possible non-standard interactions of neutrinos with matter may intricate this picture and is the subject matter of the present work. We have studied the standard parameter degeneracies in presence of non-standard interactions(NSI) with DUNE and T2HKK experiments. We examine the mass hierarchy degeneracy assuming (i) all NSI parameters to be non-zero and (ii) one NSI parameter(ǫeµ) and its corresponding CP phase(δeµ) to be non-zero. We find that the later case is more appropriate to resolve mass hierarchy degeneracy with neutrino beam energy range 1 to 4 GeV with DUNE and T2HKK experiments due to relatively small uncertainties emanating from the NSI sector. We have, also, investigated the octant degeneracy with neutrino(νµ → νe) and antineutrino(νµ →νe) mode separately. We find that to resolve this degeneracy the long baseline experiment with combination of neutrino and antineutrino mode is essential. Furthermore, we have considered DUNE in conjunction with T2HKK experiment to study CP phase degeneracy due to standard(δ) and non-standard(δeµ) CP phases. We find that CP violation effects from both standard and non-standard CP phases can be disentangled for neutrino beam energy 1.5 to 7 GeV. The DUNE and T2HKK experiments show similar sensitivities to resolve standard parameter degeneracies in presence of non-standard interactions of neutrinos with matter. * sverma@cuhimachal.ac.in, s 7verma@yahoo.co.in †

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