Biggio, C., Fernandez-Martinez, E., Filaci, M., Hernandez-Garcia, J., & Lopez-Pavon, J. (2020). Global bounds on the Type-III Seesaw. J. High Energy Phys., 05(5), 022–33pp.
Abstract: We derive general bounds on the Type-III Seesaw parameters from a global fit to flavor and electroweak precision data. We explore and compare three Type-III Seesaw realizations: a general scenario, where an arbitrary number of heavy triplets is integrated out without any further assumption, and the more constrained cases in which only 3 or 2 (minimal scenario) additional heavy states are included. The latter assumption implies rather non-trivial correlations in the Yukawa flavor structure of the model so as to reproduce the neutrino masses and mixings as measured in neutrino oscillations experiments and thus qualitative differences can be found with the more general scenario. In particular, we find that, while the bounds on most elements of the dimension 6 operator coefficients are of order 10(-4) for the general and 3-triplet cases, the 2-triplet scenario is more strongly constrained with bounds between 10(-5) and 10(-7) for the different flavours. We also discuss how these correlations affect the present CMS constraints on the Type-III Seesaw in the minimal 2-triplet scenario.
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Escribano, P., Reig, M., & Vicente, A. (2020). Generalizing the Scotogenic model. J. High Energy Phys., 07(7), 097–25pp.
Abstract: The Scotogenic model is an economical setup that induces Majorana neutrino masses at the 1-loop level and includes a dark matter candidate. We discuss a generalization of the original Scotogenic model with arbitrary numbers of generations of singlet fermion and inert doublet scalar fields. First, the full form of the light neutrino mass matrix is presented, with some comments on its derivation and with special attention to some particular cases. The behavior of the theory at high energies is explored by solving the Renormalization Group Equations.
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Blennow, M., Coloma, P., Donini, A., & Fernandez-Martinez, E. (2013). Gain fractions of future neutrino oscillation facilities over T2K and NOvA. J. High Energy Phys., 07(7), 159–23pp.
Abstract: We evaluate the probability of future neutrino oscillation facilities to discover leptonic CP violation and/or measure the neutrino mass hierarchy. We study how this probability is affected by positive or negative hints for these observables to be found at T2K and NO nu A. We consider the following facilities: LBNE; T2HK; and the 10 GeV Neutrino Factory (NF10), and show how their discovery probabilities change with the running time of T2K and NO nu A conditioned to their results. We find that, if after 15 years T2K and NO nu A have not observed a 90% CL hint of CP violation, then LBNE and T2HK have less than a 10% chance of achieving a 5 sigma discovery, whereas NF10 still has a similar to 40% chance to do so. Conversely, if T2K and NO nu A have an early 90% CL hint in 5 years from now, T2HK has a rather large chance to achieve a 5 sigma CP violation discovery (75% or 55%, depending on whether the mass hierarchy is known or not). This is to be compared with the 90% (30%) probability that NF10 (LBNE) would have to observe the same signal at 5 sigma. A hierarchy measurement at 5 sigma is achievable at both LBNE and NF10 with more than 90% probability, irrespectively of the outcome of T2K and NO nu A. We also find that if LBNE or a similar very long baseline super-beam is the only next generation facility to be built, then it is very useful to continue running T2K and NO nu A (or at least T2K) beyond their original schedule in order to increase the CP violation discovery chances, given their complementarity.
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Felipe, R. G., Joaquim, F. R., & Serodio, H. (2013). Flavored CP asymmetries for type II seesaw leptogenesis. Int. J. Mod. Phys. A, 28(31), 1350165–13pp.
Abstract: A novel contribution to the leptonic CP asymmetries in type II seesaw leptogenesis scenarios is obtained for the cases in which flavor effects are relevant for the dynamics of leptogenesis. In the so-called flavored leptogenesis regime, the interference between the tree-level amplitude of the scalar triplet decaying into two leptons and the one-loop wave function correction with leptons in the loop, leads to a new nonvanishing CP asymmetry contribution. The latter conserves total lepton number but violates lepton flavor. Cases in which this novel contribution may be dominant in the generation of the baryon asymmetry are briefly discussed.
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Alcaide, J., Salvado, J., & Santamaria, A. (2018). Fitting flavour symmetries: the case of two-zero neutrino mass textures. J. High Energy Phys., 07(7), 164–18pp.
Abstract: We present a numeric method for the analysis of the fermion mass matrices predicted in flavour models. The method does not require any previous algebraic work, it offers a chi(2) comparison test and an easy estimate of confidence intervals. It can also be used to study the stability of the results when the predictions are disturbed by small perturbations. We have applied the method to the case of two-zero neutrino mass textures using the latest available fits on neutrino oscillations, derived the available parameter space for each texture and compared them. Textures A(1) and A(2) seem favoured because they give a small chi(2), allow for large regions in parameter space and give neutrino masses compatible with Cosmology limits. The other “allowed” textures remain allowed although with a very constrained parameter space, which, in some cases, could be in conflict with Cosmology. We have also revisited the “forbidden” textures and studied the stability of the results when the texture zeroes are not exact. Most of the forbidden textures remain forbidden, but textures F-1 and F-3 are particularly sensitive to small perturbations and could become allowed.
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Blankenburg, G., & Morisi, S. (2012). Fermion masses and mixing with tri-bimaximal in SO(10) with type-I seesaw. J. High Energy Phys., 01(1), 016–18pp.
Abstract: We study a class of models for tri-bimaximal neutrino mixing in SO(10) grand unified SUSY framework. Neutrino masses arise from both type-I and type-II seesaw mechanisms. We use dimension five operators in order to not spoil tri-bimaximal mixing by means of type-I contribution in the neutrino sector. We show that it is possible to fit all fermion masses and mixings including also the recent T2K result as deviation from the tri-bimaximal.
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Casas, J. A., Moreno, J. M., Rius, N., Ruiz de Austri, R., & Zaldivar, B. (2011). Fair scans of the seesaw. Consequences for predictions on LFV processes. J. High Energy Phys., 03(3), 034–22pp.
Abstract: We give a straightforward procedure to scan the seesaw parameter-space, using the common “R-parametrization”, in a complete way. This includes a very simple rule to incorporate the perturbativity requirement as a condition for the entries of the R-matrix. As a relevant application, we show that the somewhat propagated belief that BR(mu -> e, gamma) in supersymmetric seesaw models depends strongly on the value of theta(13) is an “optical effect” produced by incomplete scans, and does not hold after a careful analytical and numerical study. When the complete scan is done, BR(mu -> e, gamma) gets very insensitive to theta(13). This holds even if the right-handed neutrino masses are kept constant or under control (as is required for succesful leptogenesis). In most cases the values of BR(mu -> e, gamma) are larger than the experimental upper bound. Including (unflavoured) leptogenesis does not introduce any further dependence on theta(13), although decreases the typical value of BR(mu -> e, gamma).
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Chakraborty, K., Goswami, S., Gupta, C., & Thakore, T. (2019). Enhancing the hierarchy and octant sensitivity of ESS nu SB in conjunction with T2K, NO nu A and ICAL@INO. J. High Energy Phys., 05(5), 137–26pp.
Abstract: The main aim of the ESSSB proposal is the discovery of the leptonic CP phase (CP) with a high significance (5 sigma for 50% values of (CP)) by utilizing the physics at the second oscillation maxima of the P-e channel. It can achieve 3 sigma sensitivity to hierarchy for all values of (CP). In this work, we concentrate on the hierarchy and octant sensitivity of the ESSSB experiment. We show that combining the ESSSB experiment with the atmospheric neutrino data from the proposed India-based Neutrino Observatory (INO) experiment can result in an increased sensitivity to mass hierarchy. In addition, we also combine the results from the ongoing experiments T2K and NOa assuming their full run-time and present the combined sensitivity of ESSSB + ICAL@INO + T2K + NOA. We show that while by itself ESSSB can have up to 3 sigma hierarchy sensitivity, the combination of all the experiments can give up to 5 sigma sensitivity depending on the true hierarchy-octant combination. The octant sensitivity of ESSSB is low by itself. However the combined sensitivity of all the above experiments can give up to 3 sigma sensitivity depending on the choice of true hierarchy and octant. We discuss the various degeneracies and the synergies that lead to the enhanced sensitivity when combining different experimental data.
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Bustamante, M., Gago, A. M., & Pena-Garay, C. (2010). Energy-independent new physics in the flavour ratios of high-energy astrophysical neutrinos. J. High Energy Phys., 04(4), 066–28pp.
Abstract: We have studied the consequences of breaking the CPT symmetry in the neutrino sector, using the expected high-energy neutrino flux from distant cosmological sources such as active galaxies. For this purpose we have assumed three different hypotheses for the neutrino production model, characterised by the flavour fluxes at production phi(0)(e) : phi(0)(mu) : phi(0)(tau) = 1 : 2 : 0, 0 : 1 : 0, and 1 : 0 : 0, and studied the theoretical and experimental expectations for the muon-neutrino flux at Earth, phi(mu), and for the flavour ratios at Earth, R = phi(mu)/phi(e) and S = phi(tau)/phi(mu). CPT violation (CPTV) has been implemented by adding an energy-independent term to the standard neutrino oscillation Hamiltonian. This introduces three new mixing angles, two new eigenvalues and three new phases, all of which have currently unknown values. We have varied the new mixing angles and eigenvalues within certain bounds, together with the parameters associated to pure standard oscillations. Our results indicate that, for the models 1 : 2 : 0 and 0 : 1 : 0, it might be possible to find large deviations of phi(mu), R, and S between the cases without and with CPTV, provided the CPTV eigenvalues lie within 10(-29) – 10(-27) GeV, or above. Moreover, if CPTV exists, there are certain values of R and S that can be accounted for by up to three production models. If no CPTV were observed, we could set limits on the CPTV eigenvalues of the same order. Detection prospects calculated using IceCube suggest that for the models 1 : 2 : 0 and 0 : 1 : 0, the modifications due to CPTV are larger and more clearly separable from the standard-oscillations predictions. We conclude that IceCube is potentially able to detect CPTV but that, depending on the values of the CPTV parameters, there could be a mis-determination of the neutrino production model.
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Mandal, S., Srivastava, R., & Valle, J. W. F. (2021). Electroweak symmetry breaking in the inverse seesaw mechanism. J. High Energy Phys., 03(3), 212–28pp.
Abstract: We investigate the stability of Higgs potential in inverse seesaw models. We derive the full two-loop RGEs of the relevant parameters, such as the quartic Higgs self-coupling, taking thresholds into account. We find that for relatively large Yukawa couplings the Higgs quartic self-coupling goes negative well below the Standard Model instability scale similar to 10(10) GeV. We show, however, that the “dynamical” inverse seesaw with spontaneous lepton number violation can lead to a completely consistent and stable Higgs vacuum up to the Planck scale.
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