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Karan, A., Sadhukhan, S., & Valle, J. W. F. (2023). Phenomenological profile of scotogenic fermionic dark matter. J. High Energy Phys., 12(12), 185–34pp.
Abstract: We consider the possibility that neutrino masses arise from the exchange of dark matter states. We examine in detail the phenomenology of fermionic dark matter in the singlet-triplet scotogenic model. We explore the case of singlet-like fermionic dark matter, taking into account all coannihilation effects relevant for determining its relic abundance, such as fermion-fermion and scalar-fermion coannihilation. Although this in principle allows for dark matter below 60 GeV, the latter is in conflict with charged lepton flavour violation (cLFV) and/or collider physics constraints. We examine the prospects for direct dark matter detection in upcoming experiments up to 10 TeV. Fermion-scalar coannihilation is needed to obtain viable fermionic dark matter in the 60-100 GeV mass range. Fermion-fermion and fermion-scalar coannihilation play complementary roles in different parameter regions above 100 GeV.
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Escrihuela, F. J., Forero, D. V., Miranda, O. G., Tortola, M., & Valle, J. W. F. (2015). On the description of nonunitary neutrino mixing. Phys. Rev. D, 92(5), 053009–16pp.
Abstract: Neutrino oscillations are well established and the relevant parameters determined with good precision, except for the CP phase, in terms of a unitary lepton mixing matrix. Seesaw extensions of the Standard Model predict unitarity deviations due to the admixture of heavy isosinglet neutrinos. We provide a complete description of the unitarity and universality deviations in the light-neutrino sector. Neutrino oscillation experiments involving electron or muon neutrinos and antineutrinos are fully described in terms of just three new real parameters and a new CP phase, in addition to the ones describing oscillations with unitary mixing. Using this formalism we describe the implications of nonunitarity for neutrino oscillations and summarize the model-independent constraints on heavy-neutrino couplings that arise from current experiments.
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Chatterjee, S. S., Miranda, O. G., Tortola, M., & Valle, J. W. F. (2022). Nonunitarity of the lepton mixing matrix at the European Spallation Source. Phys. Rev. D, 106(7), 075016–16pp.
Abstract: If neutrinos get mass through the exchange of lepton mediators, as in seesaw schemes, the neutrino appearance probabilities in oscillation experiments are modified due to effective nonunitarity of the lepton mixing matrix. This also leads to new CP phases and an ambiguity in underpinning the “conventional” phase of the three-neutrino paradigm. We study the CP sensitivities of various setups based at the European Spallation Source neutrino super-beam (ESSnuSB) experiment in the presence of nonunitarity. We also examine its potential in constraining the associated new physics parameters. Moreover, we show how the combination of DUNE and ESSnuSB can help further improve the sensitivities on the nonunitarity parameters.
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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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Miranda, O. G., Tortola, M., & Valle, J. W. F. (2016). New Ambiguity in Probing CP Violation in Neutrino Oscillations. Phys. Rev. Lett., 117(6), 061804–5pp.
Abstract: If neutrinos get mass via the seesaw mechanism the mixing matrix describing neutrino oscillations can be effectively nonunitary. We show that in this case the neutrino appearance probabilities involve a new CP phase phi associated with nonunitarity. This leads to an ambiguity in extracting the “standard” three-neutrino phase delta(CP), which can survive even after neutrino and antineutrino channels are combined. Its existence should be taken into account in the planning of any oscillation experiment aiming at a robust measurement of delta(CP).
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