Arbelaez, C., Cepedello, R., Fonseca, R. M., & Hirsch, M. (2020). (g-2) anomalies and neutrino mass. Phys. Rev. D, 102(7), 075005–14pp.
Abstract: Motivated by the experimentally observed deviations from standard model predictions, we calculate the anomalous magnetic moments a(alpha) = (g – 2)(alpha) for a = e, μin a neutrino mass model originally proposed by Babu, Nandi, and Tavartkiladze (BNT). We discuss two variants of the model: the original model, and a minimally extended version with an additional hypercharge-zero triplet scalar. While the original BNT model can explain a(mu), only the variant with the triplet scalar can explain both experimental anomalies. The heavy fermions of the model can be produced at the high-luminosity LHC, and in the part of parameter space where the model explains the experimental anomalies it predicts certain specific decay patterns for the exotic fermions.
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Arbelaez, C., Fonseca, R. M., Romao, J. C., & Hirsch, M. (2013). Supersymmetric SO(10)-inspired GUTs with sliding scales. Phys. Rev. D, 87(7), 075010–19pp.
Abstract: We construct lists of supersymmetric models with extended gauge groups at intermediate steps, all of which are inspired by SO(10) unification. We consider three different kinds of setups: (i) the model has exactly one additional intermediate scale with a left-right (LR) symmetric group; (ii) SO(10) is broken to the LR group via an intermediate Pati-Salam scale; and (iii) the LR group is broken into SU(3)(c) X SU(2)(L) X U(1)(R) X U(1)(B-L), before breaking to the standard model (SM) group. We use sets of conditions, which we call the “sliding mechanism,” which yield unification with the extended gauge group(s) allowed at arbitrary intermediate energy scales. All models thus can have new gauge bosons within the reach of the LHC, in principle. We apply additional conditions, such as perturbative unification, renormalizability and anomaly cancellation and find that, despite these requirements, for the ansatz (i) with only one additional scale still around 50 different variants exist that can have a LR symmetry below 10 TeV. For the more complicated schemes (ii) and (iii) literally thousands of possible variants exist, and for scheme (ii) we have also found variants with very low Pati-Salam scales. We also discuss possible experimental tests of the models from measurements of supersymmetry masses. Assuming mSugra boundary conditions we calculate certain combinations of soft terms, called “invariants,” for the different classes of models. Values for all the invariants can be classified into a small number of sets, which contain information about the class of models and, in principle, the scale of beyond-minimal supersymmetric extension of the Standard Model physics, even in case the extended gauge group is broken at an energy beyond the reach of the LHC.
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Cordero-Carrion, I., Hirsch, M., & Vicente, A. (2019). Master Majorana neutrino mass parametrization. Phys. Rev. D, 99(7), 075019–6pp.
Abstract: After introducing a master formula for the Majorana neutrino mass matrix, we present a master parametrization for the Yukawa matrices automatically in agreement with neutrino oscillation data. This parametrization can be used for any model that induces Majorana neutrino masses. The application of the master parametrization is also illustrated in an example model, with special focus on its lepton flavor violating phenomenology.
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Fonseca, R. M., Hirsch, M., & Srivastava, R. (2018). Delta L=3 processes: Proton decay and the LHC. Phys. Rev. D, 97(7), 075026–7pp.
Abstract: We discuss lepton number violation in three units. From an effective field theory point of view, Delta L = 3 processes can only arise from dimension 9 or higher operators. These operators also violate baryon number, hence many of them will induce proton decay. Given the high dimensionality of these operators, in order to have a proton half-life in the observable range, the new physics associated to Delta L = 3 processes should be at a scale as low as 1 TeV. This opens up the possibility of searching for such processes not only in proton decay experiments but also at the LHC. In this work we analyze the relevant d = 9, 11, 13 operators which violate lepton number in three units. We then construct one simple concrete model with interesting low- and high-energy phenomenology.
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Cordero-Carrion, I., Hirsch, M., & Vicente, A. (2020). General parametrization of Majorana neutrino mass models. Phys. Rev. D, 101(7), 075032–25pp.
Abstract: We discuss a general formula which allows to automatically reproduce experimental data for Majorana neutrino mass models, while keeping the complete set of the remaining model parameters free for general scans, as necessary in order to provide reliable predictions for observables outside the neutrino sector. We provide a proof of this master parametrization and show how to apply it for several well-known neutrino mass models from the literature. We also discuss a list of special cases, in which the Yukawa couplings have to fulfill some particular additional conditions.
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