References of "Aristizabal Sierra, Diego"
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See detailRadiative Origin of Majorana Neutrino Masses
Aristizabal Sierra, Diego ULg

in PoS - Proceedings of Science (in press)

We discuss raditiative-induced neutrino mass mechanisms. We first briefly discuss systematic one-loop level classifications, and then discuss two-loop classification schemes based on a diagrammatic ... [more ▼]

We discuss raditiative-induced neutrino mass mechanisms. We first briefly discuss systematic one-loop level classifications, and then discuss two-loop classification schemes based on a diagrammatic decomposition of the Weinberg operator. We point out that both, the one and two-loop order systematic sorting provides an exhaustive guide for radiative neutrino mass models. [less ▲]

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See detailTwo-loop-induced neutrino masses: A model-independent perspective
Aristizabal Sierra, Diego ULg

in PoS - Proceedings of Science (in press)

We disucuss Majorana neutrino mass generation mechanisms at the two-loop order. After briefly reviewing the systematic classification of one-loop realizations, we then focus on a general two-loop ... [more ▼]

We disucuss Majorana neutrino mass generation mechanisms at the two-loop order. After briefly reviewing the systematic classification of one-loop realizations, we then focus on a general two-loop classification scheme which provides a model-independent catalog for neutrino mass models at the two-loop order [less ▲]

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See detailRadiative accidental matter
Da Silva Simoes, Catarina ULg; Aristizabal Sierra, Diego ULg; Wegman Ostrosky, Daniel ULg

in Journal of High Energy Physics [=JHEP] (2016)

Accidental matter models are scenarios where the beyond-the-standard model physics preserves all the standard model accidental and approximate symmetries up to a cutoff scale related with lepton number ... [more ▼]

Accidental matter models are scenarios where the beyond-the-standard model physics preserves all the standard model accidental and approximate symmetries up to a cutoff scale related with lepton number violation. We study such scenarios assuming that the new physics plays an active role in neutrino mass generation, and show that this unavoidably leads to radiatively induced neutrino masses. We systematically classify all possible models and determine their viability by studying electroweak precision data, bigbang nucleosynthesis and electroweak perturbativity, fi nding that the latter places the most stringent constraints on the mass spectra. These results allow the identi fication of minimal radiative accidental matter models for which perturbativity is lost at high scales. We calculate radiative charged-lepton flavor violating processes in these setups, and show that mu -> e gamma has a rate well within MEG sensitivity provided the lepton-number violating scale is at or below 5 105 GeV, a value (naturally) assured by the radiative suppression mechanism. Sizeable tau -> mu gamma branching fractions within SuperKEKB sensitivity are possible for lower lepton-number breaking scales. We thus point out that these scenarios can be tested not only in direct searches but also in lepton flavor-violating experiments. [less ▲]

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See detailClosing in on minimal dark matter and radiative neutrino masses
Da Silva Simoes, Catarina ULg; Aristizabal Sierra, Diego ULg; Wegman Ostrosky, Daniel ULg

in Journal of High Energy Physics [=JHEP] (2016)

We study one-loop radiative neutrino mass models in which one of the beyond-the- standard model fi elds is either a hypercharge-zero fermion quintet (minimal dark matter) or a hypercharge-zero scalar ... [more ▼]

We study one-loop radiative neutrino mass models in which one of the beyond-the- standard model fi elds is either a hypercharge-zero fermion quintet (minimal dark matter) or a hypercharge-zero scalar septet. By systematically classifying all possible one-loop such models we identify various processes that render the neutral component of these representations (dark matter) cosmologically unstable. Thus, our fi ndings show that these scenarios are in general not reconcilable with dark matter stability unless tiny couplings or additional ad hoc symmetries are assumed, in contrast to minimal dark matter models where stability is entirely due to the standard model gauge symmetry. For some variants based on higher-order loops we find that alpha_ 2 reaches a Landau pole at rather low scales, a couple orders of magnitude from the characteristic scale of the model itself. Thus, we argue that some of these variations although consistent with dark matter stability and phenomenological constraints are hard to reconcile with perturbativity criteria. [less ▲]

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See detailLong-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report, Volume 4 The DUNE Detectors at LBNF
Aristizabal Sierra, Diego ULg

Report (2016)

The LBNF/DUNE CDR describes the proposed physics program and technical designs at the conceptual design stage. At this stage, the design is still undergoing development and the CDR therefore presents a ... [more ▼]

The LBNF/DUNE CDR describes the proposed physics program and technical designs at the conceptual design stage. At this stage, the design is still undergoing development and the CDR therefore presents a reference design for each element as well as alternative designs that are under consideration. [less ▲]

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See detailDiboson anomaly: Heavy Higgs resonance and QCD vector-like exotics
Aristizabal Sierra, Diego ULg; Vicente, Avelino; Herrero-Garcia, Juan et al

in Physical Review. D : Particles and Fields (2016), 93

The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8−2.2 TeV. In the light of these ... [more ▼]

The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8−2.2 TeV. In the light of these results, we argue that such signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I Two Higgs Doublet Model. We demonstrate that in the presence of colored vector-like fermions, its gluon fusion production cross section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD "exotic" representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find: (i) a CP-odd scalar with mass below ∼2.3 TeV, (ii) new colored states with masses below ∼2 TeV, (iii) no statistically significant diboson events in the W±Z channel, (iv) events in the triboson channels W±W∓Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar. [less ▲]

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See detailRadiative origin of neutrino masses
Aristizabal Sierra, Diego ULg

in Acta Physica Polonica B (2015), 46

Mechanisms for Majorana neutrino mass generation can be classified according to the level at which the Weinberg operator is generated. The different possibilities can be sorted in “canonical” tree-level ... [more ▼]

Mechanisms for Majorana neutrino mass generation can be classified according to the level at which the Weinberg operator is generated. The different possibilities can be sorted in “canonical” tree-level and loop-induced realizations, the latter being motivated by their potential experimental testability. Here, we discuss the one- and two-loop cases, paying special attention to systematic classification schemes, whose aim is that of constructing a full picture for neutrino mass generation [less ▲]

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See detailShedding Light on the b to s Anomalies
Aristizabal Sierra, Diego ULg; Vicente, Avelino ULg; Staub, Florian

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2015), 92(015001),

The LHCb collaboration has recently reported on some anomalies in b→s transitions. In addition to discrepancies with the Standard Model (SM) predictions in some angular observables and branching ratios ... [more ▼]

The LHCb collaboration has recently reported on some anomalies in b→s transitions. In addition to discrepancies with the Standard Model (SM) predictions in some angular observables and branching ratios, an intriguing hint for lepton universality violation was found. Here we propose a simple model that extends the SM with a dark sector charged under an additional U(1) gauge symmetry. The spontaneous breaking of this symmetry gives rise to a massive Z′ boson, which communicates the SM particles with a valid dark matter candidate, while solving the b→s anomalies with contributions to the relevant observables. [less ▲]

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See detailDynamical Flavor Origin of ZN Symmetries
Aristizabal Sierra, Diego ULg; Vicente, Avelino ULg; Fong, Sheng et al

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2015), 91(9),

Discrete Abelian symmetries (ZN) are a common “artifact” of beyond the standard model physics models. They provide different avenues for constructing consistent scenarios for lepton and quark mixing ... [more ▼]

Discrete Abelian symmetries (ZN) are a common “artifact” of beyond the standard model physics models. They provide different avenues for constructing consistent scenarios for lepton and quark mixing patterns, radiative neutrino mass generation as well as dark matter stabilization. We argue that these symmetries can arise from the spontaneous breaking of the Abelian U(1) factors contained in the global flavor symmetry transformations of the gauge-invariant kinetic Lagrangian. This will be the case provided the ultraviolet completion responsible for the Yukawa structure involves scalar fields carrying nontrivial U(1) charges. Guided by minimality criteria, we demonstrate the viability of this approach with two examples: first, we derive the “scotogenic” model Lagrangian, and second, we construct a setup where the spontaneous symmetry-breaking pattern leads to a Z3 symmetry which enables dark matter stability as well as neutrino mass generation at the two-loop order. This generic approach can be used to derive many other models, with residual ZN or ZN1×⋯×ZNk symmetries, establishing an intriguing link between flavor symmetries, neutrino masses and dark matter. [less ▲]

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See detailSystematic classification of two-loop realizations of the Weinberg operator
Aristizabal Sierra, Diego ULg; Hirsch, Martin; Degée, Audrey ULg et al

in Journal of High Energy Physics [=JHEP] (2015), 2015(03),

We systematically analyze the d=5 Weinberg operator at 2-loop order. Using a diagrammatic approach, we identify two different interesting categories of neutrino mass models: (i) Genuine 2- loop models for ... [more ▼]

We systematically analyze the d=5 Weinberg operator at 2-loop order. Using a diagrammatic approach, we identify two different interesting categories of neutrino mass models: (i) Genuine 2- loop models for which both, tree-level and 1-loop contributions, are guaranteed to be absent. And (ii) finite 2-loop diagrams, which correspond to the 1-loop generation of some particular vertex appearing in a given 1-loop neutrino mass model, thus being effectively 2-loop. From the large list of all possible 2-loop diagrams, the vast majority are infinite corrections to lower order neutrino mass models and only a moderately small number of diagrams fall into these two interesting classes. Moreover, all diagrams in class (i) are just variations of three basic diagrams, with examples discussed in the literature before. Similarly, we also show that class (ii) diagrams consists of only variations of these three plus two more basic diagrams. Finally, we show how our results can be consistently and readily used in order to construct two-loop neutrino mass models. [less ▲]

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See detailLong-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF
Aristizabal Sierra, Diego ULg

Report (2015)

The global neutrino physics community is developing a multi-decade physics program to measure unknown parameters of the Standard Model of particle physics and search for new phenomena. The program will be ... [more ▼]

The global neutrino physics community is developing a multi-decade physics program to measure unknown parameters of the Standard Model of particle physics and search for new phenomena. The program will be carried out as an international, leading-edge, dual-site experiment for neutrino science and proton decay studies, which is known as the Deep Underground Neutrino Experiment (DUNE). The detectors for this experiment will be designed, built, commissioned and operated by the international DUNE Collaboration. The facility required to support this experiment, the Long-Baseline Neutrino Facility (LBNF), is hosted by Fermilab and its design and construction is organized as a DOE/Fermilab project incorporating international partners. Together LBNF and DUNE will comprise the world’s highest-intensity neutrino beam at Fermilab, in Batavia, IL, a high-precision near detector on the Fermilab site, a massive liquid argon time-projection chamber (LArTPC) far detector installed deep underground at the Sanford Underground Research Facility (SURF) 1300 km away in Lead, SD, and all of the conventional and technical facilities necessary to support the beamline and detector systems. [less ▲]

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See detailExplaining the CMS Higgs lepton-flavor violating
Aristizabal Sierra, Diego ULg; Vicente, Avelino ULg

in Physical Review. D : Particles and Fields (2014), 90(11), 115004

Direct searches for lepton flavor violating Higgs boson decays in the τ μ channel have been recently reported by the CMS collaboration. The results display a slight excess of signal events with a ... [more ▼]

Direct searches for lepton flavor violating Higgs boson decays in the τ μ channel have been recently reported by the CMS collaboration. The results display a slight excess of signal events with a significance of 2.5σ, which translates into a branching ratio of about 1%. By interpreting these findings as a hint for beyond the standard model physics, we show that the Type-III 2HDM is capable of reproducing such signal while at the same time satisfying vacuum stability, perturbativity, electroweak precision data, measured Higgs standard decay modes and low-energy lepton flavor violating constraints. We have found that the allowed signal strength ranges for the bb, WW* and ZZ* standard channels shrink as soon as BR(h→τμ)∼ 1% is enforced. Thus, we point out that if the excess persists, improved measurements of these channels may be used to test our Type-III 2HDM scenario. [less ▲]

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See detailScalar triplet flavored leptogenesis: a systematic approach
Aristizabal Sierra, Diego ULg; Dhen, Mikael; Hambye, Thomas

in Journal of Cosmology and Astroparticle Physics (2014), 2014

Type-II seesaw is a simple scenario in which Majorana neutrino masses are generated by the exchange of a heavy scalar electroweak triplet. When endowed with additional heavy fields, such as right-handed ... [more ▼]

Type-II seesaw is a simple scenario in which Majorana neutrino masses are generated by the exchange of a heavy scalar electroweak triplet. When endowed with additional heavy fields, such as right-handed neutrinos or extra triplets, it also provides a compelling framework for baryogenesis via leptogenesis. We derive in this context the full network of Boltzmann equations for studying leptogenesis in the flavored regime. To this end we determine the relations which hold among the chemical potentials of the various particle species in the thermal bath. This takes into account the standard model Yukawa interactions of both leptons and quarks as well as sphaleron processes which, depending on the temperature, may be classified as faster or slower than the Universe Hubble expansion. We find that when leptogenesis is enabled by the presence of an extra triplet, lepton flavor effects allow the production of the B-L asymmetry through lepton number conserving CP asymmetries. This scenario becomes dominant as soon as the triplets couple more to leptons than to standard model scalar doublets. In this case, the way the B-L asymmetry is created through flavor effects is novel: instead of invoking the effect of L-violating inverse decays faster than the Hubble rate, it involves the effect of L-violating inverse decays slower than the Hubble rate. We also analyze the more general situation where lepton number violating CP asymmetries are present and actively participate in the generation of the B-L asymmetry, pointing out that as long as L-violating triplet decays are still in thermal equilibrium when the triplet gauge scattering processes decouple, flavor effects can be striking, allowing to avoid all washout suppression effects from seesaw interactions. In this case the amount of B-L asymmetry produced is limited only by a universal gauge suppression effect, which nevertheless goes away for large triplet decay rates. [less ▲]

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See detailReactor mixing angle from hybrid neutrino masses
Aristizabal Sierra, Diego ULg; de Medeiros Varzielas, Ivo

in Journal of High Energy Physics [=JHEP] (2014), 2014(7),

In terms of its eigenvector decomposition, the neutrino mass matrix (in the basis where the charged lepton mass matrix is diagonal) can be understood as originating from a tribimaximal dominant structure ... [more ▼]

In terms of its eigenvector decomposition, the neutrino mass matrix (in the basis where the charged lepton mass matrix is diagonal) can be understood as originating from a tribimaximal dominant structure with small deviations, as demanded by data. If neutrino masses originate from at least two different mechanisms, referred to as "hybrid neutrino masses", the experimentally observed structure naturally emerges provided one mechanism accounts for the dominant tribimaximal structure while the other is responsible for the deviations. We demonstrate the feasibility of this picture in a fairly model-independent way by using lepton-number-violating effective operators, whose structure we assume becomes dictated by an underlying A4 flavor symmetry. We show that if a second mechanism is at work, the requirement of generating a reactor angle within its experimental range always fixes the solar and atmospheric angles in agreement with data, in contrast to the case where the deviations are induced by next-to-leading order effective operators. We prove this idea is viable by constructing an A4-based ultraviolet completion, where the dominant tribimaximal structure arises from the type-I seesaw while the subleading contribution is determined by either type-II or type-III seesaw driven by a non-trivial A4 singlet (minimal hybrid model). After finding general criteria, we identify all the ZN symmetries capable of producing such A4-based minimal hybrid models. [less ▲]

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See detailCloistered Baryogenesis
Aristizabal Sierra, Diego ULg; Fong, Chee Sheng; Nardi, Enrico et al

in Journal of Cosmology and Astroparticle Physics (2014), 2014

The cosmological matter-antimatter asymmetry can arise from the baryon number conserving CP asymmetry in two body decays of heavy particles, when the two final states carry equal and opposite baryon ... [more ▼]

The cosmological matter-antimatter asymmetry can arise from the baryon number conserving CP asymmetry in two body decays of heavy particles, when the two final states carry equal and opposite baryon number, and one couples directly or indirectly to electroweak sphalerons so that its baryon asymmetry gets partly reprocessed into a lepton asymmetry, while the other remains chemically decoupled from the thermal bath with its baryon content frozen. After sphaleron switchoff the decay of the decoupled particles inject in the thermal plasma an unbalanced baryon asymmetry, giving rise to baryogenesis. We highlight the features of this mechanism in a type-I seesaw model extended by adding a new colored scalar coupled to the heavy Majorana neutrinos. If the colored scalar has an O(TeV) mass, it would leave at the LHC a characteristic signature throughout all layers of the detectors. [less ▲]

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See detailLeptogenesis with a dynamical seesaw scale
Aristizabal Sierra, Diego ULg; Tortola, Maria; Valle, Jose et al

in Journal of Cosmology and Astroparticle Physics (2014), 2014

In the simplest type-I seesaw leptogenesis scenario right-handed neutrino annihilation processes are absent. However, in the presence of new interactions these processes are possible and can affect the ... [more ▼]

In the simplest type-I seesaw leptogenesis scenario right-handed neutrino annihilation processes are absent. However, in the presence of new interactions these processes are possible and can affect the resulting B-L asymmetry in an important way. A prominent example is provided by models with spontaneous lepton number violation, where the existence of new dynamical degrees of freedom can play a crucial role. In this context, we provide a model-independent discussion of the effects of right-handed neutrino annihilations. We show that in the weak washout regime, as long as the scattering processes remain slow compared with the Hubble expansion rate throughout the relevant temperature range, the efficiency can be largely enhanced, reaching in some cases maximal values. Moreover, the B-L asymmetry yield turns out to be independent upon initial conditions, in contrast to the ''standard'' case. On the other hand, when the annihilation processes are fast, the right-handed neutrino distribution tends to a thermal one down to low temperatures, implying a drastic suppression of the efficiency which in some cases can render the B-L generation mechanism inoperative. [less ▲]

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See detailLSP sneutrino decays
Aristizabal Sierra, Diego ULg; Restrepo, Diego; Spinner, Sogee

in Journal of High Energy Physics [=JHEP] (2013), 1305

In bilinear R-parity violation (BRpV), in which the superpotential includes a bilinear term between the lepton doublet and the up-type Higgs superfields, a sneutrino LSP can decay into pairs of heavy ... [more ▼]

In bilinear R-parity violation (BRpV), in which the superpotential includes a bilinear term between the lepton doublet and the up-type Higgs superfields, a sneutrino LSP can decay into pairs of heavy standard model states: W's, Z's, tops or Higgs bosons. These finals states can dominate over the traditionally considered bottom pair final state. This would lead to unique and novel supersymmetric signals with each supersymmetric event possibly producing two pairs of these heavy standard model fields. We investigate this possibility and find that the branching ratio into heavier states dominates when the bilinear term is much smaller than the sneutrino vacuum expectation value for a given sneutrino flavor. When BRpV is the only source of neutrino masses these decays can only dominate for one of the sneutrino generations. Relaxing this constraint opens these channels for all three generations. [less ▲]

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See detailScalar triplet leptogenesis without right-handed neutrino decoupling
Aristizabal Sierra, Diego ULg

in Nuclear Physics B Proceedings Supplement (2013, April), 237-238

We discuss leptogenesis in the context of type-II seesaw in the case in which in addition to the scalar electroweak triplet decays the lepton asymmetry is also induced by right-handed neutrino decays ... [more ▼]

We discuss leptogenesis in the context of type-II seesaw in the case in which in addition to the scalar electroweak triplet decays the lepton asymmetry is also induced by right-handed neutrino decays (mild hierarchical scenarios). We show that within this setup, depending on the relative sizes of the relevant parameters, one can identify three classes of generic models, each one with its own consequences for leptogenesis. [less ▲]

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See detailEigenvector-based approach to neutrino mixing
Aristizabal Sierra, Diego ULg; Houet, Eric; Ivo, Medeiros Varzielas

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2013), 87

We propose a model-independent analysis of the neutrino mass matrix through an expansion in terms of the eigenvectors defining the lepton mixing matrix, which we show can be parametrized as small ... [more ▼]

We propose a model-independent analysis of the neutrino mass matrix through an expansion in terms of the eigenvectors defining the lepton mixing matrix, which we show can be parametrized as small perturbations of the tribimaximal mixing eigenvectors. This approach proves to be powerful and convenient for some aspects of lepton mixing, in particular when studying the sensitivity of the mass matrix elements to departures from their tribimaximal form. In terms of the eigenvector decomposition, the neutrino mass matrix can be understood as originating from a tribimaximal dominant structure with small departures determined by data. By implementing this approach to cases when the neutrino masses originate from different mechanisms, we show that the experimentally observed structure arises very naturally. We thus claim that the observed deviations from the tribimaximal mixing pattern might be interpreted as a possible hint of a ``hybrid'' nature of the neutrino mass matrix. [less ▲]

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See detailLepton flavor violation and seesaw symmetries
Aristizabal Sierra, Diego ULg

in Hyperfine Interactions (2013, February), 214

When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1)R Abelian factor. In the context of minimal seesaw models we ... [more ▼]

When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1)R Abelian factor. In the context of minimal seesaw models we analyze the implications of a slightly broken U(1)R symmetry on charged lepton flavor violating decays. We find, depending on the R-charge assignments, models where charged lepton flavor violating rates can be within measurable ranges. In particular, we show that in the resulting models due to the structure of the light neutrino mass matrix muon flavor violating decays are entirely determined by neutrino data (up to a normalization factor) and can be sizable in a wide right-handed neutrino mass range. [less ▲]

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