arXiv subjects

Oscar Vives

Publications and source records attributed to Oscar Vives.

At least 19 recordsLinked to original sources

arXiv2026

Anatomy and Phenomenology of Minimal Flavor Deconstruction in the Lepton Sector

We investigate the low-energy phenomenology of a minimal flavor-deconstructed framework in the lepton sector within an effective field theory approach, focusing on the interplay between flavor and CP violation. Starting from the ultraviolet completion of the model, we derive the effective Yukawa structure through a systematic spurion expansion beyond leading order and identify the dominant sources of flavor and CP violation. We show that, while leading-order effects to dipole operators are approximately aligned with the Yukawa matrices, next-to-leading order contributions generically induce physical CP-violating phases and flavor misalignment, leading to potentially observable low-energy signals. After constructing the corresponding low-energy effective theory, we analyze the phenomenological implications for charged lepton flavor violating observables, lepton flavor universality tests, and electric dipole moments (EDMs). We find that future searches for $\mu-e$ conversion and the electron EDM can probe scales in the multi-10~TeV range under natural assumptions on the flavor structure and CP phases. Our results highlight the complementarity between flavor-violating and CP-violating observables and demonstrate that precision measurements in the lepton sector provide a powerful probe of flavor-deconstructed scenarios beyond the direct reach of collider experiments.

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arXiv2025

Beyond the Standard Model contributions to dipole moments

The goal of this work is to provide a pedagogical introduction to dipole moments and dipole transitions in theories beyond the Standard Model, with a focus on the lepton sector. We emphasize the exceptional sensitivity of dipole observables to new physics, analyzing the most sensitive processes, such as the muon anomalous magnetic moment, the electric dipole moment of the electron, and the branching ratio $\text{BR}(μ\to e γ)$. This review is intended for PhD students, early-career researchers, and anyone entering the field for the first time. It does not aim to provide a complete overview of all models in the literature, but rather to serve as an accessible guide, using simple and representative examples from the most well-studied extensions of the Standard Model.

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arXiv2025

Asymmetric Dark Matter in SUSY with approximate $R-$symmetry

We implement the asymmetric dark matter framework, linking the ordinary and dark matter abundances, within a supersymmetric context. We consider a supersymmetric model that respects an approximate $U(1)_R$ symmetry, which is broken in such a way that at high temperature the $R$ breaking sector mediate processes in equilibrium, but at the SUSY mass scale, the sparticles asymmetry is frozen. In this framework, the gravitino serves as the dark matter candidate, and its mass is predicted to be $\sim10$ GeV to match the observed relic abundance. We identify several realistic spectra; however, the requirement for the Next-to-Lightest Supersymmetric Particle (NLSP) to decay into the gravitino before Big Bang Nucleosynthesis constrains the viable spectrum to masses above 2 TeV.

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arXiv2024

Electric Dipole Moments as indirect probes of Dark Sectors

Dark sectors provide beyond Standard Model scenarios which can address unresolved puzzles, such as the observed dark matter abundance or the baryon asymmetry of the Universe. A naturally small portal to the dark sector is obtained if dark-sector interactions stem from a non-Abelian hidden gauge group that couples through kinetic mixing with the hypercharge boson. In this work, we investigate the phenomenology of such a portal of dimension five in the presence of CP violation, focusing on its signatures in fermion electric dipole moments. We show that, currently unbounded regions of the parameter space from dark photon searches can be indirectly probed with upcoming electron dipole moment experiments for dark boson masses in the range $1-100$ GeV. We also discuss two particular scenarios where a $SU(2)_D$ dark gauge group spontaneously breaks into either an Abelian $U(1)_D$ or nothing. In both cases, we show that potentially observable electron dipole moments can be produced in vast regions of the parameter space compatible with current experimental constraints and observed dark matter abundance.

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arXiv2023

Flavon vacuum alignment beyond SUSY

In flavor models the vacuum alignment of flavons is typically achieved via the $F$-terms of certain fields in the supersymmetric limit. We propose a method for preserving such alignments, up to a rescaling of the vacuum expectation values, even after supersymmetry (and the flavor symmetry) are softly broken, facilitating the vacuum alignment in models which are non-supersymmetric at low energies. Examples of models with different flavor groups, namely $A_4$, $T_7$, $S_4$ and $Δ(27)$, are discussed.

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arXiv2022

Constraining Low-Scale Flavor Models with $\boldsymbol{(g-2)_μ}$ and Lepton Flavor Violation

We present here two concrete examples of models where a sub-TeV scale breaking of their respective $\mathcal{T}_{13}$ and $A_5$ flavor symmetries is able to account for the recently observed discrepancy in the muon anomalous magnetic moment, $(g-2)_μ$. Similarities in the flavor structures of the charged-lepton Yukawa matrix and dipole matrix yielding $(g-2)_μ$ give rise to strong constraints on low-scale flavor models when bounds from lepton flavor violation (LFV) are imposed. These constraints place stringent limits on the off-diagonal Yukawa structure, suggesting a mostly (quasi-)diagonal texture for models with a low flavor breaking scale $Λ_f$. We argue that many of the popular flavor models in the literature designed to explain the fermion masses and mixings are not suitable for reproducing the observed discrepancy in $(g-2)_μ$, which requires a delicate balance of maintaining a low flavor scale while simultaneously satisfying strong LFV constraints.

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arXiv2021

Implications of the Muon g-2 result on the flavour structure of the lepton mass matrix

The confirmation of the discrepancy with the Standard Model predictions in the anomalous magnetic moment by the Muon g-2 experiment at Fermilab points to a low scale of new physics. Flavour symmetries broken at low energies can account for this discrepancy but these models are much more restricted, as they would also generate off-diagonal entries in the dipole moment matrix. Therefore, if we assume that the observed discrepancy in the muon $g-2$ is explained by the contributions of a low-energy flavor symmetry, lepton flavour violating processes can constrain the structure of the lepton mass matrices and therefore the flavour symmetries themselves predicting these structures. We apply these ideas to several discrete flavour symmetries popular in the leptonic sector, such as $Δ(27)$, $A_4$, and $A_5 \ltimes {\rm CP}$.

hep-ph↗

arXiv2020

Muon and electron $g-2$ and lepton masses in flavor models

The stringent experimental bound on $μ\rightarrow e γ$ is compatible with a simultaneous and sizable new physics contribution to the electron and muon anomalous magnetic moments $(g-2)_\ell$ ($\ell=e,\,μ$), only if we assume a non-trivial flavor structure of the dipole operator coefficients. We propose a mechanism in which the realization of the $(g-2)_\ell$ correction is manifestly related to the mass generation through a flavor symmetry. A radiative flavon correction to the fermion mass gives a contribution to the anomalous magnetic moment. In this framework, we introduce a chiral enhancement from a non-trivial $\mathcal{O}(1)$ quartic coupling of the scalar potential. We show that the muon and electron anomalies can be simultaneously explained in a vast region of the parameter space with predicted vector-like mediators of masses as large as $M_χ\in [0.6,2.5]$~TeV.

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arXiv2018

Controlled flavor violation in the MSSM from a unified $Δ(27)$ flavor symmetry

We study the phenomenology of a unified supersymmetric theory with a flavor symmetry $Δ(27)$. The model accommodates quark and lepton masses, mixing angles and CP phases. In this model, the Dirac and Majorana mass matrices have a unified texture zero structure in the $(1,1)$ entry that leads to the Gatto-Sartori-Tonin relation between the Cabibbo angle and ratios of the masses in the quark sectors, and to a natural departure from zero of the $θ_{13}^\ell$ angle in the lepton sector. We derive the flavor structures of the trilinears and soft mass matrices, and show their general non-universality. This causes large flavor violating effects. As a consequence, the parameter space for this model is constrained, allowing it to be (dis)proven by flavor violation searches in the next decade. Although the results are model specific, we compare them to previous studies to show similar flavour effects (and associated constraints) are expected in general in supersymmetric flavor models, and may be used to distinguish them.

hep-ph↗

arXiv2018

Can measurements of 2HDM parameters provide hints for high scale supersymmetry?

Two-Higgs-doublet models (2HDMs) are minimal extensions of the Standard Model (SM) that may still be discovered at the LHC. The quartic couplings of their potentials can be determined from the measurement of the masses and branching ratios of their extended scalar sectors. We show that the evolution of these couplings through renormalization group equations can determine whether the observed 2HDM is a low energy manifestation of a more fundamental theory, as for instance, supersymmetry, which fixes the quartic couplings in terms of the gauge couplings. At leading order, the minimal supersymmetric extension of the SM (MSSM) dictates all the quartic couplings, which can be translated into a predictive structure for the scalar masses and mixings at the weak scale. Running these couplings to higher scales, one can check if they converge to their MSSM values, and more interestingly, whether one can infer the supersymmetry breaking scale. Although we study this question in the context of supersymmetry, this strategy could be applied to any theory whose ultraviolet completion unambiguously predicts all scalar quartic couplings.

hep-ph↗

arXiv2017

Slepton Non-Universality in the Flavor-Effective MSSM

Supersymmetric theories supplemented by an underlying flavor-symmetry $\mathcal{G}_f$ provide a rich playground for model building aimed at explaining the flavor structure of the Standard Model. In the case where supersymmetry breaking is mediated by gravity, the soft-breaking Lagrangian typically exhibits large tree-level flavor violating effects, even if it stems from an ultraviolet flavor-conserving origin. Building on previous work, we continue our phenomenological analysis of these models with a particular emphasis on leptonic flavor observables. We consider three representative models which aim to explain the flavor structure of the lepton sector, with symmetry groups $\mathcal{G}_f = Δ(27)$, $A_4,$ and $S_3$.

hep-ph↗

arXiv2017

Effective Theories of Flavor and the Non-Universal MSSM

Flavor symmetries à la Froggatt-Nielsen~(FN) provide a compelling way to explain the hierarchies of fermionic masses and mixing angles in the Yukawa sector. In Supersymmetric~(SUSY) extensions of the Standard Model where the mediation of SUSY breaking occurs at scales larger than the breaking of flavor, this symmetry must be respected not only by the Yukawas of the superpotential, but by the soft-breaking masses and trilinear terms as well. In this work we show that contrary to naive expectations, even starting with completely flavor blind soft-breaking in the full theory at high scales, the low-energy sfermion mass matrices and trilinear terms of the effective theory, obtained upon integrating out the heavy mediator fields, are strongly non-universal. We explore the phenomenology of these SUSY flavor models after the latest LHC searches for new physics.

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arXiv2012

Cold Positrons from Decaying Dark Matter

Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often heavier particles decay into the lightest dark matter particle as the Universe evolves. Here we explore the possibilities that arise if one of the products in a (Heavy Particle) $\rightarrow$ (Dark Matter) decay is a positron, and the lifetime is shorter than the age of the Universe. The positrons cool down by scattering off the cosmic microwave background and eventually annihilate when they fall into Galactic potential wells. The resulting 511 keV flux not only places constraints on this class of models but might even be consistent with that observed by the INTEGRAL satellite.

astro-ph.CO↗

arXiv2011

Correlation between flavour violating decay of long-lived slepton and tau in the coannihilation scenario with Seesaw mechanism

We investigate flavour violating decays of the long-lived lightest slepton and the tau lepton in the coannihilation region of the Minimal Supersymmetric Standard Model with a Seesaw mechanism to generate neutrino masses. We consider a situation where the mass difference between the lightest neutralino, as the Lightest Supersymmetric particle (LSP), and the lightest slepton, as the Next-to-LSP, is smaller than the mass of tau lepton. In this situation, the lifetime of the lightest slepton is very long and it is determined by lepton flavour violating (LFV) couplings because the slepton mainly consists of the lighter stau and the flavour conserving 2-body decay is kinematically forbidden. We show that the lifetime can change many orders of magnitude by varying the Yukawa couplings entering the Seesaw mechanism. We also show that branching ratio of LFV tau decays are strongly correlated with the lightest slepton lifetime. Therefore the branching ratios of LFV tau decays can be determined or constrained by measuring the slepton lifetime at the LHC experiment.

hep-ph↗

arXiv2010

The degenerate gravitino scenario

In this work, we explore the "degenerate gravitino" scenario where the mass difference between the gravitino and the lightest MSSM particle is much smaller than the gravitino mass itself. In this case, the energy released in the decay of the next to lightest sypersymmetric particle (NLSP) is reduced. Consequently the cosmological and astrophysical constraints on the gravitino abundance, and hence on the reheating temperature, become softer than in the usual case. On the other hand, such small mass splittings generically imply a much longer lifetime for the NLSP. We find that, in the constrained MSSM (CMSSM), for neutralino LSP or NLSP, reheating temperatures compatible with thermal leptogenesis are reached for small splittings of order 10^{-2} GeV. While for stau NLSP, temperatures of 4x10^9 GeV can be obtained even for splittings of order of tens of GeVs. This "degenerate gravitino" scenario offers a possible way out to the gravitino problem for thermal leptogenesis in supersymmetric theories.

hep-ph↗

arXiv2008

Measuring Lepton Flavour Violation at LHC with Long-Lived Slepton in the Coannihilation Region

When the mass difference between the lightest slepton, the NLSP, and the lightest neutralino, the LSP, is smaller than the tau mass, the lifetime of the lightest slepton increases in many orders of magnitude with respect to typical lifetimes of other supersymmetric particles. These small mass differences are possible in the MSSM and, for instance, they correspond to the coannihilation region of the CMSSM for $M_{1/2} \gsim 700$ GeV. In a general gravity-mediated MSSM, where the lightest supersymmetric particle is the neutralino, the lifetime of the lightest slepton is inversely proportional to the square of the intergenerational mixing in the slepton mass matrices. Such a long-lived slepton would produce a distinctive signature at LHC and a measurement of its lifetime would be relatively simple. Therefore, the long-lived slepton scenario offers an excellent opportunity to study lepton flavour violation at ATLAS and CMS detectors in the LHC and an improvement of the leptonic mass insertion bounds by more than five orders of magnitude would be possible.

hep-ph↗

arXiv2008

Light charged Higgs at the beginning of the LHC era

The terascale will be explored with the start of the LHC. One of the most fundamental questions which we expect to be answered is the root of electroweak symmetry breaking and whether the Higgs mechanism is realized in nature or not. In this context we pose the question if existing experimental data still allow for a light non-minimal Higgs sector. We tackle this question first in the context of the two Higgs doublet model and then we concentrate in two supersymmetric models, the constrained MSSM and the MSSM with non-universal Higgs masses. In both supersymmetric scearios, light pseudoscalar and light charged-Higgs bosons are still viable provided tan beta is large. In this regime, we emphasize the importance of the constraints provided by the decay B to tau nu mediated by the charged-Higgs at tree-level. In addition we comment on generic predictions for hadronic colliders and indirect searches in such scenarios.

hep-ph↗

arXiv2007

Flavour symmetries and SUSY soft breaking in the LHC era

The so-called supersymmetric flavour problem does not exist in isolation to the Standard Model flavour problem. We show that a realistic flavour symmetry can simultaneously solve both problems without ad hoc modifications of the SUSY model. Furthermore, departures from the SM expectations in these models can be used to discriminate among different possibilities. In particular we present the expected values for the electron EDM in a flavour model solving the supersymmetric flavour and CP problems.

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