arXiv subjects

Eduardo Peinado

Publications and source records attributed to Eduardo Peinado.

At least 19 recordsLinked to original sources

arXiv2026

Insights into 1-loop corrections to neutrino low-scale type-I seesaw mechanism

The standard type-I seesaw can also be regarded as a low-scale seesaw by using the freedom of the Casas-Ibarra parameterization. In this framework, radiative corrections to the neutrino mass matrix can dominate over the tree-level contribution, so that the tree-level Casas-Ibarra construction no longer solves the equation that determines the physical neutrino masses and mixings. We show how the Casas-Ibarra parametrization can be consistently extended to this loop-corrected equation, by reabsorbing the 1-loop corrections into the right-handed neutrino mass matrix, so that the resulting light neutrino mass matrix is consistent with experimental values. On the other hand, we show that physical processes related to right-handed neutrino propagation, such as heavy neutral lepton searches, do not depend on the 1-loop corrections. Moreover, we show that ${\rm Br}(μ\to e γ)$ provides competitive constraints on the parameter space of heavy neutral lepton search experiments for masses above $100$ GeV.

hep-ph↗

arXiv2026

Minimalist Seesaw-Scotogenic Mechanism as a Source for Neutrino Physics

We identify the smallest discrete flavor symmetry and minimal field content that can simultaneously account for neutrino masses and the dark sector in the context of the discrete dark matter. Minimality is achieved with a $D_4$ symmetry by adding three right-handed neutrinos and three scalar doublets. Within this framework, tree-level and one-loop contributions yield the observed solar--atmospheric mass splitings as well as the observed neutrino mixings. Furthermore, by including CP-violating phases, the model successfully accommodates both normal and inverted ordering. Spontaneous $D_4$ breaking leaves a residual $\mathbb{Z}_2$ symmetry that stabilizes the dark matter candidate, with a predicted mass within the $50$--$200$ GeV range, consistent with LUX-ZEPLIN limits.

hep-ph↗

arXiv2026

Constraints on Light Sterile Neutrinos and Scalar Non-Standard Interactions Using the First Reactor Antineutrino Oscillation Results at JUNO

Constraints on light sterile neutrinos and scalar non-standard neutrino interactions are obtained from the first reactor antineutrino results reported by JUNO. The analysis is based on a spectral $χ^2$ fit to the prompt-energy distribution corresponding to 59.1 days of data, including full three-flavor oscillations extended to a $3+1$ framework and effective scalar NSI contributions. The reactor flux is modeled using the Daya Bay measured spectrum, and systematic uncertainties are accounted for through a set of nuisance parameters describing reactor flux normalization, spectral shape, background normalization, and detector response. It is found that JUNO is already sensitive to light sterile neutrinos in the mass-splitting range $10^{-5} \lesssim Δm^2_{41}/\text{eV}^2 \lesssim 10^{-2}$, probing mixing amplitudes down to $\sin^2 2θ_{14} \sim \mathcal{O}(10^{-1})$. In addition, a constraint on the scalar NSI parameter $|η_{ee}| < \mathcal{O}(10^{-2})$ is obtained, with correlations with solar oscillation parameters. These results demonstrate the potential of JUNO to probe small deviations from the Standard Model resulting from new physics through precision measurements, with significant improvements expected as statistics and systematic control improve.

hep-ph↗

arXiv2026

Dirac neutrinos and gauged lepton number

We propose the first scotogenic neutrino mass model with gauged lepton number $U(1)_L$, which is spontaneously broken by three units $ΔL=3$ down to a residual discrete gauge symmetry $\mathbb{Z}_6$. The latter guarantees that neutrinos acquire tiny Dirac masses via a one-loop scotogenic mechanism, simultaneously stabilizing the lightest electrically neutral particle with non-trivial charge under the preserved $\mathbb{Z}_6$ symmetry. In our model there is a scalar particle identified as weakly interacting massive particle dark matter (DM) candidate. We analyzed its compatibility with the existing data on direct DM detection experiments and the DM relic abundance. We also address charged lepton flavor violating decays in our model and find that their predicted rates are within the reach of current experimental sensitivity.

hep-ph↗

arXiv2025

Axionless strong CP problem solution: the spontaneous CP violation case

We propose an alternative to the axion mechanism for addressing the charge parity (CP) problem in quantum chromodynamics (QCD). Our approach involves imposing CP as an inherent symmetry of the Lagrangian, which is then spontaneously broken. To generate the correct texture for the Yukawa matrices, we introduce a discrete $\mathbb{Z}_2$ symmetry that is softly broken by the scalar potential. By identifying a benchmark point for the Yukawa couplings that aligns with the measured quark masses, the CKM matrix, and low-energy flavor-changing constraints, our findings suggest that this model offers a viable solution to the CP problem.

hep-ph↗

arXiv2025

Exploring the Standard Model and Beyond from the Evidence of CE$ν$NS with Reactor Antineutrinos in CONUS+

The observation of the Coherent Elastic Neutrino-Nucleus Scattering (CE$ν$NS) process using reactor antineutrinos offers a unique opportunity to probe the Standard Model and explore Beyond the Standard Model scenarios. This study reports on the latest results from the CONUS+ experiment conducted at the Leibstadt nuclear power plant (KKL), Switzerland. The CONUS collaboration reports $395 \pm 106$ events detected from reactor antineutrinos with an exposure of 347 kg$\cdot$days, utilizing high-purity germanium detectors operated at sub-keV thresholds. A $χ^2$-based statistical analysis was performed on these results, incorporating systematic uncertainties. This analysis was used to extract the weak mixing angle, establish a limit on the neutrino magnetic moment, and impose constraints on neutrino non-standard interactions using reactor antineutrinos. The results confirm the potential of CE$ν$NS experiments in the study of fundamental neutrino properties and probing new physics.

hep-ph↗

arXiv2024

Dark matter for Majorana neutrinos in a $\mathbb{Z}_4$ symmetry

In the minimal Scotogenic model with fermionic dark matter, the neutrino Yukawa matrix is fine-tuned to satisfy current bounds on $μ\rightarrow e γ$ while producing dark matter through thermal freeze-out. One way to avoid this bound is to open a new annihilation channel for dark matter (DM) with a scalar field that breaks the lepton number spontaneously. This introduces a physical Goldstone boson $a$, which can constitute a light relic and opens up the lepton flavor violating channel $μ\rightarrow e a$. In this work, we introduce a model that contains the new annihilation channel for fermionic dark matter but avoids the introduction of the Goldstone boson by using a discrete $\mathbb{Z}_4$ instead of a continuous symmetry. In this way, cosmological constraints on the light relic and experimental limits on lepton flavor violating decays to the Goldstone boson are avoided. We analyze the experimental viability of the model, identifying the region of parameter space where lepton flavor violating constraints are not saturated, DM has the correct relic density, and DM direct detection experiments are sensitive to the DM candidate.

hep-ph↗

arXiv2024

The $L_μ-L_τ$ solution to the IceCube Ultra High Energy neutrino deficit in light of NA64

In this work we analyze the scenario where a MeV scale $L_μ- L_τ$ gauge boson can explain the deficit in the diffuse ultra high energy (UHE) astrophysical neutrino spectrum observed in IceCube, as well as the discrepancy between experimental and $e^+e^-$ dispersion data driven SM calculations of the muon anomalous magnetic moment. We map the parameter space of the model where the elastic resonant s-channel scattering of UHE neutrinos with the cosmic neutrino background, mediated by the new Z', can improve the description of the observed cascade and track spectra over the no-scattering hypothesis. Comparing to recent NA64$μ$ results, we find that some part of the parameter space remains unexplored, but at a data volume of $10^{11}$ muons on target NA64$μ$ will completely probe this region.

hep-ph↗

arXiv2024

Two-zero textures for Dirac Neutrinos

We review the two-zero mass matrix textures approach for Dirac neutrinos with the most recent global fit in the oscillation parameters. We found that three of the 15 possible textures are compatible with current experimental data, while the remaining two-zero textures are ruled out. Two textures are consistent with the neutrino masses' normal hierarchy and are CP-conserving. At the same time, the other one is compatible with both mass orderings and allows for CP violation. We also present the correlations between the oscillation parameters for the allowed two-zero textures.

hep-ph↗

arXiv2024

Non-unitary limits on different textures for low-scale seesaw models

New heavy neutral leptons lead to non-unitary effects in models for neutrino masses. Such effects could represent a sign of new physics beyond the Standard Model, leading to observable deviations in neutrino oscillation experiments, lepton flavor violation, and other precision measurements. This work explores the parameter space of the linear and inverse low-scale seesaw models based on flavor symmetries consistent with neutrino oscillation experiments. In particular, we investigated the violation of unitarity when the lepton flavor violation is absent and when only one lepton flavor-violating channel is present.

hep-ph↗

arXiv2024

Quantization of Second Order Fermions

The quantization of a massive spin $1/2$ field that satisfies the Klein-Gordon equation is studied. The framework is consistent, provided it is formulated as a pseudo-hermitian quantum field theory by the redefinition of the field dual and the identification of an operator that modifies the inner product of states in Hilbert space to preserve a real energy spectrum and unitary evolution. Since the fermion field has mass dimension one, the theory admits renormalizable fermion self-interactions.

hep-th↗

arXiv2023

Closing the dark photon window to thermal dark matter

The nature of dark matter remains a central question in particle physics, cosmology, and astrophysics. The prevailing hypothesis postulates that dark matter consists of particles that interact only weakly with Standard Model particles. However, the knowledge of dark matter properties beyond these interactions is limited. This study explores a scenario involving a dark photon as a mediator between dark matter and the Standard Model, akin to the photon's role in electromagnetism. Recent cosmological and experimental evidence impose constraints on this scenario, focusing on results from direct detection experiments such as PICO-60, XENON-1T, and PANDAX-4T. The results reveal severe constraints, effectively closing the window for laboratory searches for dark photons as mediators between the Standard Model and the dark sector (dark electrons) in the secluded dark matter scenario. The findings underscore the need for alternative explanations and offer fresh perspectives on the ongoing quest to understand dark matter and its interactions since they are nearly independent of the dark electron fraction content for the total dark matter. This analysis significantly narrows down the parameter space for thermal dark matter scenarios involving a dark photon portal, reinforcing the urgency of exploring alternative models and designing new experiments to unravel the mysteries surrounding the nature of dark matter.

hep-ph↗

arXiv2023

Discrete dark matter mechanism as the source of neutrino mass scales

The hierarchy in scale between atmospheric and solar neutrino mass splittings is investigated through two distinct neutrino mass mechanisms, from tree- and one-loop-level contributions. We demonstrate that the minimal discrete dark matter mechanism contains the ingredients for explaining this hierarchy. This scenario is characterized by adding new RH neutrinos and scalar $SU(2)$-doublets to the Standard Model as triplet representations of an $A_4$ flavor symmetry. The $A_4$ symmetry breaking, which occurs at the electroweak scale, leads to a residual $\mathbb{Z}_2$ symmetry responsible for the dark matter stability and dictates the neutrino phenomenology. Finally, we show that to reproduce the neutrino mixing angles correctly it is necessary to violate CP in the scalar potential.

hep-ph↗

arXiv2023

Neutrino mass hierarchy from the discrete dark matter model

We explore a possible explanation for the hierarchy in scale between the atmospheric and solar neutrino mass differences ($\lvert Δm^{2}_{31} \rvert$, and $Δm^{2}_{21}$) through the presence of two distinct neutrino mass mechanisms from tree- and one-loop-level contributions. We demonstrate that the ingredients needed to explain this hierarchy are present in the minimal discrete dark matter model [arXiv:2301.10811]. This scenario is characterized by adding new RH neutrinos and scalar $SU(2)$ doublets to the Standard Model as triplet representations of an $A_4$ flavour symmetry. The $A_4$ symmetry breaking, which occurs at the electroweak scale, leads to a residual $\mathbb{Z}_2$ symmetry responsible for the dark matter stability and dictates the neutrino phenomenology. We show that CP breaking in the scalar potential is needed to fit the neutrino mixing angles.

hep-ph↗

arXiv2022

Neutrino masses and self-interacting dark matter with mass mixing $Z-Z^\prime$ gauge portal

New light gauge bosons can affect several low-energy experiments, such as atomic parity violation or colliders. Here, we explore the possibility that a dark sector is charged under a new $U(1)$ gauge symmetry, and the portal to the Standard Model is through a $Z-Z'$ mass mixing. In our approach, breaking the new gauge symmetry is crucial to generate neutrino masses. We investigate the parameter space to reproduce neutrino masses, the correct dark matter relic abundance, and to produce the observed core-like DM distribution in galactic centers.

hep-ph↗

arXiv2022

CE$ν$NS as a probe of flavored generalized neutrino interactions

We examine the potential to probe generalized neutrino interactions (GNI), exotic effective couplings due to new physics interactions beyond the Standard Model, in the coherent-elastic neutrino-nucleus scattering experiments in light of the latest COHERENT-CsI, and -LAr data. Our analysis focuses on scalar, vector and tensor flavored-GNI parameters. A combined analysis has been made to constrain these exotic couplings for the CsI and LAr detector. We further add the projected forthcoming reactor-based Scintillating Bubble Chamber detector to examine these couplings. It has been observed that the addition of reactor data strongly constrained electron flavor GNI.

hep-ph↗

arXiv2022

New Physics searches in a low threshold scintillating argon bubble chamber measuring coherent elastic neutrino-nucleus scattering in reactors

The sensitivity to New Physics of a low threshold scintillating argon bubble chamber measuring coherent elastic neutrino-nucleus scattering in reactors is reported. Namely, light scalar mediators, sterile neutrino oscillations, unitarity violation, and non-standard interactions are studied. The results indicate that this detector could be able to set stronger constraints than current limits set by the recent COHERENT measurements. Considering the best scenario, a 100 kg detector located 30 m from a 2000 MW$_{th}$ reactor, a sterile neutrino search would cover most of the space parameter allowed from the reactor anti-neutrino anomaly fit. Unitarity violation studies could set constraints on $α_{11}$ more stringent than the current oscillation experiments fit. A low threshold argon detector with very low backgrounds has the potential to explore New Physics in different scenarios and set competitive constraints.

hep-ph↗

arXiv2021

Complementarity between dark matter direct searches and CE$ν$NS experiments in $U(1)'$ models

We explore the possibility of having a fermionic dark matter candidate within $U(1)'$ models for CE$ν$NS experiments in light of the latest COHERENT data and the current and future dark matter direct detection experiments. A vector-like fermionic dark matter has been introduced which is charged under $U(1)'$ symmetry, naturally stable after spontaneous symmetry breaking. We perform a complementary investigation using CE$ν$NS experiments and dark matter direct detection searches to explore dark matter as well as $Z^{\prime}$ boson parameter space. Depending on numerous other constraints arising from the beam dump, LHCb, BABAR, and the forthcoming reactor experiment proposed by the SBC collaboration, we explore the allowed region of $Z^{\prime}$ portal dark matter.

hep-ph↗