To understand the observed pattern of neutrino masses and mixing as well as to account for the dark matter we propose a hybrid scoto-seesaw model based on the A4 discrete flavor symmetry. In this setup, including at least two heavy right-handed neutrinos is essential to employ the discrete flavor symmetry that mimics once popular tribimaximal neutrino mixing at the leading order via type-I seesaw. The scotogenic contribution then acts as a critical deviation to reproduce the observed value of the reactor mixing angle θ13 (within the trimaximal mixing scheme) and to accommodate potential dark matter candidates, pointing towards a common origin of θ13 and dark matter. The model predicts the atmospheric angle to be in the upper octant, excludes some regions on the Dirac CP phase, and restricts the Majorana phases too. Further, normal and inverted mass hierarchies can be distinguished for specific values of the relative phases associated with the complex light neutrino mass matrix. Owing to the considered flavor symmetry, contributions coming from the scotogenic mechanism towards the lepton flavor violating decays such as μ → eγ, τ → eγ vanish, and a lower limit on the second right-handed neutrino mass can be obtained. Prediction for the effective mass parameter appearing in the neutrinoless double beta decay falls within the sensitivity of future experiments such as LEGEND-1k and nEXO.

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In this work, we have considered an extension of the standard model (SM) with a SU (2) L singlet vector-like quark (VLQ) with electric charge Q = +2/3. The model also contains an additional U (1) d local symmetry group under which all the SM particles are neutral. Even though in this model the VLQ possesses many properties qualitatively similar to that of the traditional top partner (T p ), there are some compelling differences as well. In particular, its branching ratio to the traditional modes (T p → bW, tZ, th) are suppressed which in turn helps to evade many of the existing bound, mainly coming from the LHC experiments. In an earlier work, such a VLQ is referred to as 'maverick top partner'. It has been shown that the top partner in this model predominantly decays to a top quark and a dark photon/dark higgs pair over a large region of the parameter space. The dark photon can be made invisible and consequently, it gives rise to the missing transverse energy signature at the LHC detector. We have mainly focused on the LHC signatures and future prospects of such 'maverick top partners'. In particular, we have studied the t t + missing transverse energy and t + missing transverse energy signatures in the context of the LHC via single and pair productions of the top partner, respectively at 13 and 14 TeV LHC center of mass energies assuming that the dark photon is invisible either at the length scale of the detector or it decays into an invisible mode. We have shown that one can exclude sin θ L ∼ 0.03 (0.05) for m Tp 1.8 (2.6) TeV at √ s = 14 TeV with an integrated luminosity of 3 ab −1 using the single top partner production channel.

In this work, we have modified a scenario, originally proposed by Grimus and Lavoura, in order to obtain maximal values for atmospheric mixing angle and $CP$ violating Dirac phase of the lepton sector. To achieve this, we have employed $CP$ and some discrete symmetries in a type II seesaw model. In order to make predictions about neutrino mass ordering and the smallness of the reactor angle, we have obtained some conditions on the elements of the neutrino mass matrix of our model. Finally, within the framework of our model, we have studied quark masses and mixing pattern. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.