We present a measurement of angular observables and a test of lepton flavor universality in the B → K * + − decay, where is either e or µ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb −1 containing 772 × 10 6 B B pairs, collected at the Υ(4S) resonance with the Belle detector at the asymmetric-energy e + e − collider KEKB. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.

Within the framework of residual symmetry, two Z 2 type associate µτ interchange symmetries robustly constrain the Dirac CP phase δ in a model independent way. Both of them predict simultaneous maximality of δ and the atmospheric mixing angle θ 23 . We show how these well known correlations will be changed if we generalize the µτ interchange symmetry to a µτ mixing symmetry. In particular, we show that the stringent condition of simultaneous maximality could be relaxed even with a very small departure from the exact µτ interchange. In addition, the present neutrino data on δ and θ 23 can be explained better by the mixing symmetry. After discussing the impact of the µτ mixing in some realistic neutrino mass models, we show how the proposed mixing could be realized with two simultaneous CP transformations which also lead to novel and testable correlations between δ and the mixing angles θ ij . Next we discuss in particular, the 'three flavour regime' of leptogenesis within the CP extended framework and show, unlike the ordinary CP extended µτ interchange symmetry, a resonant leptogenesis is possible due the generalization of µτ interchange to the µτ mixing and the produced baryon asymmetry always requires a nonmaximal θ 23 owing to the fact that the baryon to photon ratio η B vanishes in the exact limit of θ 23 = π/4. This is one of the robust prediction of this framework. The CP extended µτ mixing is also a novel example of a low energy effective model which provides an important insight to the off-diagonal terms of the flavour coupling matrix which have usually been neglected in literature to compute the final baryon asymmetry, in particular in the models with flavour symmetries. * R.Samanta@soton.ac.uk

Abstract:We investigate the consequences of a generalized Z 2 ×Z 2 symmetry on a scaling neutrino Majorana mass matrix. It enables us to determine definite analytical relations between the mixing angles θ 12 and θ 13 , maximal CP violation for the Dirac type and vanishing for the Majorana type. Beside the other testable predictions on the low energy neutrino parameters such as ββ 0ν decay matrix element |M ee | and the light neutrino masses m 1,2,3 , the model also has intriguing consequences from the perspective of leptogenesis. With the assumption that the required CP violation for leptogenesis is created by the decay of lightest (N 1 ) of the heavy Majorana neutrinos, only τ -flavored leptogenesis scenario is found to be allowed in this model. For a normal (inverted) ordering of light neutrino masses, θ 23 is found be less (greater) than its maximal value, for the final baryon asymmetry Y B to be in the observed range. Besides, an upper and a lower bound on the mass of N 1 have also been estimated. Effect of the heavier neutrinos N 2,3 on final Y B has been worked out subsequently. The predictions of this model will be tested in the experiments such as nEXO, LEGEND, GERDA-II, T2K, NOνA, DUNE etc.

We investigate Linear and Inverse seesaw mechanisms with maximal zero textures of the constituent matrices subjected to the assumption of non-zero eigenvalues for the neutrino mass matrix m ν and charged lepton mass matrix m e . If we restrict to the minimally parametrized non-singular 'm e ' (i.e., with maximum number of zeros) it gives rise to only 6 possible textures of m e . Non-zero determinant of m ν dictates six possible textures of the constituent matrices. We ask in this minimalistic approach, what are the phenomenologically allowed maximum zero textures are possible. It turns out that Inverse seesaw leads to 7 allowed two-zero textures while the Linear seesaw leads to only one. In Inverse seesaw, we show that 2 is the maximum number of independent zeros that can be inserted into µ S to obtain all 7 viable two-zero textures of m ν . On the other hand, in Linear seesaw mechanism, the minimal scheme allows maximum 5 zeros to be accommodated in 'm' so as to obtain viable effective neutrino mass matrices (m ν ). Interestingly, we find that our minimalistic approach in Inverse seesaw leads to a realization of all the phenomenologically allowed two-zero textures whereas in Linear seesaw only one such texture is viable. Next our numerical analysis shows that none of the two-zero textures give rise to enough CP violation or significant δ CP . Therefore, if δ CP = π/2 is established, our minimalistic scheme may still be viable provided we allow more number of parameters in 'm e '. * roopam.sinha@saha.ac.in † rome.samanta@saha.ac.in ‡ ambar.ghosal@saha.ac.in 1 arXiv:1508.05227v2 [hep-ph]

We propose a complex extension of mixed µτ antisymmetry in the neutrino Majorana mass matrix M ν . This can be implemented in the Lagrangian by a generalized CP transformation (labeled by a mixing parameter θ) on the left-chiral flavor neutrino fields. We investigate its implications for leptonic CP violation and neutrino phenomenology in general. Interestingly, the µτ mixing parameter θ gets correlated with the Dirac CP phase δ and the atmospheric mixing angle θ 23 through an analytical relation. In general, for arbitrary θ, both θ 23 and δ are nonmaximal. We discuss the corresponding results for the CP asymmetry parameter A µe in neutrino oscillation experiments. For a nonmaximal δ, one of the two Majorana phases is different from 0 or π, thereby leading to nonvanishing Majorana CP violation with observable consequences for the neutrinoless double beta (ββ0ν) decay process. We numerically work out in detail the predictions for that process in relation to various ongoing and forthcoming experiments. We also work out the predictions of our scheme on flavor flux ratios at neutrino telescopes. While exact CP transformed µτ interchange antisymmetry (θ = π/2) leads to an exact equality among those ratios, taking a value 0.5, a tiny deviation can cause a drastic change in them. Careful measurement of these flux ratios in future will further constrain the parameter θ.