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- More about unphysical zeroes in quark mass matricesPublication . Costa, David Emmanuel; Gonzalez Felipe, RicardoWe look for all weak bases that lead to texture zeroes in the quark mass matrices and contain a minimal number of parameters in the framework of the standard model. Since there are ten physical observables, namely, six nonvanishing quark masses, three mixing angles and one CP phase, the maximum number of texture zeroes in both quark sectors is altogether nine. The nine zero entries can only be distributed between the up- and down-quark sectors in matrix pairs with six and three texture zeroes or five and four texture zeroes. In the weak basis where a quark mass matrix is nonsingular and has six zeroes in one sector, we find that there are 54 matrices with three zeroes in the other sector, obtainable through right-handed weak basis transformations. It is also found that all pairs composed of a nonsingular matrix with five zeroes and a nonsingular and nondecoupled matrix with four zeroes simply correspond to a weak basis choice. Without any further assumptions, none of these pairs of up- and down-quark mass matrices has physical content. It is shown that all non-weak-basis pairs of quark mass matrices that contain nine zeroes are not compatible with current experimental data. The particular case of the so-called nearest-neighbour-interaction pattern is also discussed.
- Flavored asymmetries for type II seesaw leptogenesisPublication . Gonzalez Felipe, Ricardo; Joaquim, F. R.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.
- Combining texture zeros with a remnant CP symmetry in the minimal type-I seesawPublication . Barreiros, Debora; Gonzalez Felipe, Ricardo; Joaquim, FilipeIn the framework of the two right-handed neutrino seesaw model, we consider maximally-restrictive texture-zero patterns for the lepton Yukawa coupling and mass matrices, together with the existence of a remnant CP symmetry. Under this premise, we find that several textures are compatible with the most recent data coming from neutrino oscillation and neutrinoless double beta decay experiments. It is shown that, the maximum number of allowed texture zeros in the Dirac Yukawa coupling matrix is two, for an inverted neutrino mass spectrum. In contrast, for Yukawa coupling matrices with just one texture zero, both normal and inverted orderings of neutrino masses are compatible with data. In all cases, the predictions for the low-energy Dirac and Majorana CP-violating phases, and for the effective mass parameter relevant in neutrinoless double-beta decay experiments, are presented and discussed. We also comment on the impact of future experimental improvements in scrutinising texture-zero patterns with a remnant CP symmetry, within the minimal version of the seesaw mechanism considered here.
- Dirac neutrinos in the 2HDM with restrictive Abelian symmetriesPublication . Correia, S. S.; Gonzalez Felipe, Ricardo; Joaquim, F. R.Recently, there has been a growing interest in extensions of the Standard Model in which naturally small Dirac neutrino masses arise due to existence of a symmetry which protects neutrino's Diracness. Motivated by this, we consider an extension of the Standard Model with a second Higgs doublet (2HDM) and three right-handed neutrinos where lepton number is conserved and, thus, neutrinos are Dirac particles. In this framework, we identify the most restrictive texture-zero combinations for the Dirac-neutrino and chargedlepton mass matrices that lead to masses and mixings compatible with current experimental data. We then investigate, in a systematic way, which of these combinations can be realized by Abelian continuous U(1) or discrete Z(N) symmetries. We conclude that, from the 28 initially possible sets of maximally-restricted lepton mass matrices, only 5 have a symmetry realization in the 2HDM. For these cases, one-to-one relations among the Yukawa couplings and the neutrino mass and mixing parameters are established, and the fermion interactions with the neutral and charged scalars of the 2HDM are also determined. Consequences for lepton universality in tau decays and rare lepton-flavor-violating processes are also discussed.
- Minimal inverse-seesaw mechanism with Abelian flavour symmetriesPublication . Camara, Henrique B.; Gonzalez Felipe, Ricardo; Joaquim, F. R.We study the phenomenology of the minimal (2, 2) inverse-seesaw model supplemented with Abelian flavour symmetries. To ensure maximal predictability, we establish the most restrictive flavour patterns which can be realised by those symmetries. This setup requires adding an extra scalar doublet and two complex scalar singlets to the Standard Model, paving the way to implement spontaneous CP violation. It is shown that such CP-violating effects can be successfully communicated to the lepton sector through couplings of the scalar singlets to the new sterile fermions. The Majorana and Dirac CP phases turn out to be related, and the active-sterile neutrino mixing is determined by the active neutrino masses, mixing angles and CP phases. We investigate the constraints imposed on the model by the current experimental limits on lepton flavour-violating decays, especially those on the branching ratio BR(mu -> e gamma) and the capture rate CR(mu - e, Au). The prospects to further test the framework put forward in this work are also discussed in view of the projected sensitivities of future experimental searches sensitive to the presence of heavy sterile neutrinos. Namely, we investigate at which extent upcoming searches for mu -> e gamma, mu -> 3e and mu - e conversion in nuclei will be able to test our model, and how complementary will future high-energy collider and beam-dump experiments be in that task.
- Preface: 9th international workshop on astronomy and relativistic astrophysics: From quarks to cosmosPublication . Zen Vasconcellos, Cesar Augusto; Hess, Peter Otto; Piccinelli, Gabriella; Vargas-Magana, Mariana; Urena-Lopez, Luis Arturo; Gonzalez Felipe, Ricardo; Boller, Thomas; Gullberg, StevenWe outline our experience in organizing the 9th edition of the International Workshop on Astronomy and Relativistic Astrophysics: from Quarks to Cosmos, in virtual format, denominated IWARA2020 Video Conference, held from 6 to 12 September, 2020. The IWARA 2020 Video Conference aimed to bring together leading academic scientists, professors, students, and research scholars for exchanging experiences and research results and discuss the most recent innovations, trends, concerns, practical challenges, and solutions adopted in the research fields within the scope of the conference. The IWARA 2020 Video Conference offered to the participants a platform for scientific and academic projects, partnerships, and presentation of high-quality research contributions describing original and unpublished results on several topics related as new phenomena and new states of matter in the Universe, general relativity, gravitation, cosmology, dwarf stars, neutron and exotic stars, pulsars, black holes, GRBs, astroparticles and nuclear physics, QCD and heavy-ion reactions, quantum gravity and quantum cosmology, gravitational-wave astronomy, dark energy, dark matter, strange matter, high-energy cosmic rays, galaxies, blazars and quasars, strong magnetic fields in the Universe as well as laboratories, observatories, telescopes, and other experimental and observational facilities that will define the future directions of astrophysics, astronomy, cosmology, nuclear and astroparticle physics and the future of physics at the energy frontiers, and topics related to these.
- Scalar-singlet assisted leptogenesis with CP violation from the vacuumPublication . Barreiros, Debora; Câmara, Henrique B.; Gonzalez Felipe, Ricardo; Joaquim, FilipeIn the vanilla type-I seesaw leptogenesis scenario, CP violation required to generate the lepton asymmetries in the heavy Majorana neutrino decays stem from complex Dirac-type Yukawa couplings. In this paper we explore the case in which that CP violation originates from the vacuum expectation value of a complex scalar singlet at a very high scale. This non-trivial CP-violating phase can be successfully communicated to the low-energy neutrino sector via the heavy neutrino portal. The new scalar-singlet degrees of freedom generate new contributions to the CP asymmetries relevant for leptogenesis not only at the one-loop level but also through tree-level three-body decays. These are computed here for an arbitrary number of heavy neutrinos, Higgs doublets and scalar singlets. We also take into account the new decays and scattering processes that enter the unflavoured Boltzmann equations governing the heavy-neutrino particle densities and the (B - L)-asymmetry evolution. Having established the framework of interest, we present a simple model with two RH neutrinos, two Higgs doublets and a complex scalar singlet, supplemented with a ?(8) flavour symmetry. This symmetry minimises the number of free parameters without compromising the possibility of spontaneous CP violation and compatibility with neutrino data. In fact, the only viable ?(8) charge assignment shows a preference for a non-trivial spontaneous CP-violating phase, which in turn leads to a non-vanishing CP asymmetry due to the direct link between high- and low-energy CP violation. An interesting feature of this simple setup is that the usual wave and vertex type-I seesaw contributions to the CP asymmetry vanish due to the ?(8) symmetry. Thus, the observed baryon-to-photon ratio can be explained thanks to the new couplings among the heavy neutrinos and the new scalar degrees of freedom.
- Quantum magnetic collapse of a partially bosonized npe-gas: Implications for astrophysical jetsPublication . Gonzalez Felipe, Ricardo; Martinez, A. Perez; Rojas, H. Perez; Quintero Angulo, GretelWe study the quantum magnetic collapse of a partially bosonized npe-gas and obtain that this type of collapse might be one of the mechanisms behind matter expulsion out of compact objects. We check also that this gas might form a stable stream of matter whose collimation is due to its strong self-generated magnetic field. Possible astrophysical applications of these results, in particular related to jet formation and its maintenance, are discussed.
- Minimal type-I seesaw model with maximally restricted texture zerosPublication . Barreiros, Debora; Gonzalez Felipe, Ricardo; Joaquim, FilipeIn the context of Standard Model (SM) extensions, the seesaw mechanism provides the most natural explanation for the smallness of neutrino masses. In this work we consider the most economical type-I seesaw realization in which two right-handed neutrinos are added to the SM field content. For the sake of predictability, we impose the maximum number of texture zeros in the lepton Yukawa and mass matrices. All possible patterns are analyzed in the light of the most recent neutrino oscillation data, and predictions for leptonic CP violation are presented. We conclude that, in the charged-lepton mass basis, eight different texture combinations are compatible with neutrino data at 1 sigma, all of them for an inverted-hierarchical neutrino mass spectrum. Four of these cases predict a CP-violating Dirac phase close to 3 pi/2, which is around the current best-fit value from the global analysis of neutrino oscillation data. If one further reduces the number of free parameters by considering three equal elements in the Dirac neutrino Yukawa coupling matrix, several texture combinations are still compatible with data but only at 3 sigma. For all viable textures, the baryon asymmetry of the Universe is computed in the context of thermal leptogenesis, assuming (mildly) hierarchical heavy Majorana neutrino masses M-1,M-2. It is shown that the flavored regime is ruled out, while the unflavored one requires M-1 similar to 10(14) GeV.
- Maximally restrictive leptonic texture zeros in two-Higgs-doublet modelsPublication . Gonzalez Felipe, Ricardo; Serodio, HugoThe implementation of maximally restrictive texture zeros in the leptonic sector is investigated in the context of two-Higgs-doublet models with Majorana neutrinos. After analyzing all maximally restrictive pairs of leptonic mass matrices with zero entries, we conclude that there are only four texture combinations that are compatible with observations at 3σ confidence level and can be implemented through Abelian symmetries in a two-Higgs-doublet model. The compatibility of these textures with current constraints on leptonflavor-violating processes is also studied. The ultraviolet completion of these models is discussed in the framework of the seesaw mechanism for neutrino masses.