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Hirsch, M., Morisi, S., Peinado, E., & Valle, J. W. F. (2010). Discrete dark matter. Phys. Rev. D, 82(11), 116003–5pp.
Abstract: We propose a new motivation for the stability of dark matter (DM). We suggest that the same non-Abelian discrete flavor symmetry which accounts for the observed pattern of neutrino oscillations, spontaneously breaks to a Z(2) subgroup which renders DM stable. The simplest scheme leads to a scalar doublet DM potentially detectable in nuclear recoil experiments, inverse neutrino mass hierarchy, hence a neutrinoless double beta decay rate accessible to upcoming searches, while theta(13) = 0 gives no CP violation in neutrino oscillations.
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Morisi, S., Peinado, E., Shimizu, Y., & Valle, J. W. F. (2011). Relating quarks and leptons without grand unification. Physical Review D, 84(3), 036003.
Abstract: In combination with supersymmetry, flavor symmetry may relate quarks with leptons, even in the absence of a grand-unification group. We propose an SU(3) x SU(2) x U(1) model where both supersymmetry and the assumed A(4) flavor symmetries are softly broken, reproducing well the observed fermion mass hierarchies and predicting: (i) a relation between down-type quarks and charged lepton masses, and (ii) a correlation between the Cabibbo angle in the quark sector and the reactor angle theta(13) characterizing CP violation in neutrino oscillations.
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Morisi, S., Patel, K. M., & Peinado, E. (2011). Model for T2K indication with maximal theta(23) and trimaximal theta(12). Phys. Rev. D, 84(5), 053002–6pp.
Abstract: Recently T2K experiment gives hint in favor of large reactor angle theta(13). Most of the models, with tribimaximal mixing at the leading order, can not reproduce such a large mixing angle since they predict typically corrections for the reactor angle of the order theta(13) similar to lambda(2)(C), where lambda(C) similar to 0.2. In this paper, we discuss the possibility to achieve large theta(13) within the T2K region with maximal atmosphericmixing angle, sin(2)theta(23) = 1/2, and trimaximal solar mixing angle, sin(2)theta(12) = 1/3, through the deviation from the exact tribimaximal mixing. We derive the structure of neutrino mass matrix that leads to the large theta(13) leaving maximal theta(23) and trimaximal theta(12). It is shown that such a structure of neutrino mass matrix can arise in a model with S(4) flavor symmetry.
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Mazumdar, A., & Morisi, S. (2012). Split neutrinos, two Majorana and one Dirac, and implications for leptogenesis, dark matter, and inflation. Phys. Rev. D, 86(4), 045031–6pp.
Abstract: We propose a simple framework to split neutrinos with a slight departure from tribimaximal-where two of the neutrinos are Majorana type which provide thermal leptogenesis. We propose a model based on S-3 flavor symmetry. The Dirac neutrino with a tiny Yukawa coupling explains primordial inflation and the cosmic microwave background radiation, where the inflaton is the gauge invariant flat direction. The observed baryon asymmetry, and the scale of inflation are intimately tied to the observed reactor angle sin theta(13), which can be further constrained by the LHC and the 0 nu beta beta experiments. The model also provides the lightest right-handed sneutrino as a part of the inflaton to be the dark matter candidate.
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Boucenna, M. S., Morisi, S., Tortola, M., & Valle, J. W. F. (2012). Bilarge neutrino mixing and the Cabibbo angle. Phys. Rev. D, 86(5), 051301–4pp.
Abstract: Recent measurements of the neutrino mixing angles cast doubt on the validity of the so-far popular 2 tribimaximal mixing Ansatz. We propose a parametrization for the neutrino mixing matrix where the reactor angle seeds the large solar and atmospheric mixing angles, equal to each other in first approximation. We suggest such a bilarge mixing pattern as a model-building standard, realized when the leading order value of theta(13) equals the Cabibbo angle lambda(C).
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Dorame, L., Morisi, S., Peinado, E., Valle, J. W. F., & Rojas, A. D. (2012). New neutrino mass sum rule from the inverse seesaw mechanism. Phys. Rev. D, 86(5), 056001–9pp.
Abstract: A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum rules. One of these implies a lower bound on the effective neutrinoless double beta mass parameter, even for normal hierarchy neutrinos. Here we propose a new model based on the S-4 flavor symmetry that leads to the new neutrino mass sum rule and discuss how to generate a nonzero value for the reactor angle theta(13) indicated by recent experiments, and the resulting correlation with the solar angle theta(12).
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Boucenna, M. S., Morisi, S., Peinado, E., Valle, J. W. F., & Shimizu, Y. (2012). Predictive discrete dark matter model and neutrino oscillations. Phys. Rev. D, 86(7), 073008–5pp.
Abstract: Dark matter stability can be achieved through a partial breaking of a flavor symmetry. In this framework we propose a type-II seesaw model where left-handed matter transforms nontrivially under the flavor group Delta(54), providing correlations between neutrino oscillation parameters, consistent with the recent Daya-Bay and RENO reactor angle measurements, as well as lower bounds for neutrinoless double beta decay. The dark matter phenomenology is provided by a Higgs-portal.
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Ding, G. J., Morisi, S., & Valle, J. W. F. (2013). Bilarge neutrino mixing and Abelian flavor symmetry. Phys. Rev. D, 87(5), 053013–13pp.
Abstract: We explore two bilarge neutrino mixing Anzatze within the context of Abelian flavor symmetry theories: (BL1) sin theta(12) similar to lambda, sin theta(13) similar to lambda, sin theta(23) similar to lambda, and (BL2) sin theta(12) similar to lambda, sin theta(13) similar to lambda, sin theta(23) similar to 1 – lambda. The first pattern is proposed by two of us and is favored if the atmospheric mixing angle theta(23) lies in the first octant, while the second one is preferred for the second octant of theta(23). In order to reproduce the second texture, we find that the flavor symmetry should be U(1) x Z(m), while for the first pattern the flavor symmetry should be extended to U(1) x Z(m) x Z(n) with m and n of different parity. Explicit models for both mixing patterns are constructed based on the flavor symmetries U(1) x Z(3) x Z(4) and U(1) x Z(2). The models are extended to the quark sector within the framework of SU(5) grand unified theory in order to give a successful description of quark and lepton masses and mixing simultaneously. Phenomenological implications are discussed.
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Forero, D. V., Morisi, S., Romao, J. C., & Valle, J. W. F. (2013). Neutrino mixing with revamped A(4) flavor symmetry. Phys. Rev. D, 88(1), 016003–7pp.
Abstract: We suggest a minimal extension of the simplest A(4) flavor model that can induce a nonzero theta(13) value, as required by recent neutrino oscillation data from reactors and accelerators. The predicted correlation between the atmospheric mixing angle theta(23) and the magnitude of theta(13) leads to an allowed region substantially smaller than indicated by neutrino-oscillation global fits. Moreover, the scheme correlates CP violation in neutrino oscillations with the octant of the atmospheric mixing parameter theta(23) in such a way that, for example, maximal mixing necessarily violates CP. We briefly comment on other phenomenological features of the model.
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Morisi, S., Nebot, M., Patel, K. M., Peinado, E., & Valle, J. W. F. (2013). Quark-lepton mass relation and CKM mixing in an A(4) extension of the minimal supersymmetric standard model. Phys. Rev. D, 88(3), 036001–8pp.
Abstract: An interesting mass relation between down-type quarks and charged leptons has been recently predicted within a supersymmetric SU(3)(c) circle times SU(2)(L) circle times U(1)(Y) model based on the A(4) flavor symmetry. Here we propose a simple extension which provides an adequate full description of the quark sector. By adding a pair of vectorlike up quarks, we show how the CKM entries V-ub, V-cb, V-td and V-ts arise from deviations of the unitarity. We perform an analysis including the most relevant observables in the quark sector, such as oscillations and rare decays of kaons, B-d and B-s mesons. In the lepton sector, the model predicts an inverted hierarchy for the neutrino masses, leading to a potentially observable rate of neutrinoless double beta decay.
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