arXiv subjects

J. Julio

Publications and source records attributed to J. Julio.

17 recordsLinked to original sources

arXiv2026

Identifying the origin of the 146-GeV excess at the LHC

The 146-GeV excess in the electron-muon final state reported by the CMS Collaboration offers a tantalizing hint for new physics. There are two competing explanations for the origin of the 146-GeV resonance: production via mixing with the Standard Model Higgs boson and leptophilic production through sea electrons and muons inside the proton. In anticipation that such an excess may still persist by the end of LHC Run 3, we propose three related production channels $H\gamma$, $H j$, and $H jj$, which could be used to distinguish between these two possible scenarios. Taking the two-Higgs-doublet model (2HDM) as an explicit example, we estimate that with $3000~\text{fb}^{-1}$ of the high-luminosity LHC data, the $H\gamma$ channel can provide a striking discriminating power between the mixing and leptophilic scenarios with a significance of 7.1. Combining it with the other two channels, $H j$ and $H jj$, the significance can be pushed up to 7.6.

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arXiv2025

Constraining the new contributions to electron $g-2$ in a radiative neutrino mass model

We examine electron and muon anomalous magnetic dipole moments within a radiative neutrino mass model featuring TeV-scale scalar leptoquarks $S(3,1,-1/3)$ and $R(3,2,1/6)$. We utilize textures with decoupling electron and muon sectors, so that both electron and muon anomalous magnetic dipole moments could receive internal chiral enhancements from different heavy up-type quarks while in the same time evading the stringent $\mu\to e\gamma$ constraint. A successful fit to neutrino oscillation data requires the simultaneous presence of one- and two-loop neutrino mass contributions. This severely constrains the parameter space of the model, which results in a negligible new physics correction to the muon $g-2$. The electron $g-2$ discrepancy implied by the rubidium experiment, on the other hand, can be resolved within $2\sigma$ uncertainty provided that neutrino mass ordering is inverted. Lepton-flavor-violating tau decay rates, such as $\tau\to e\gamma$ and $\tau\to 3e$, are predicted to be within the sensitivities of next-generation experiments.

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arXiv2025

Novel probes for electron-muon flavor violation from exotic Higgs decays

In this paper, we propose two novel signatures of Higgs decays to search for electron-muon flavor violation. These signatures arise from the presence of a light pseudoscalar into which the 125-GeV Higgs boson decays. The pseudoscalar subsequently decays into an electron-muon pair, leading to multilepton final states, which are relatively clean signatures to search for at the LHC. As a benchmark, we consider the type-III Two-Higgs-doublet-model. We analyze both low-energy and collider constraints on the model and identify regions of parameter space where the light pseudoscalar is viable. Our proposed signatures yield stronger constraints on the lepton flavor violating couplings than current low-energy precision measurements. Taken together, our findings suggest that collider-based probes of exotic Higgs decays provide a powerful complement to precision experiments in the quest to uncover new physics.

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arXiv2024

Electron EDM and $\Gamma(\mu \to e \gamma)$ in the 2HDM

We present the first complete two-loop calculation of the electric dipole moment of the electron, as well as the rates of the lepton-flavor violating decays $\mu \to e + \gamma$ and $\tau \to e/\mu + \gamma$, in the unconstrained two-Higgs doublet model. We include the most general Yukawa interactions of the Higgs doublets with the Standard Model fermions up to quadratic order, and allow for generic phases in the Higgs potential. A python implementation of our results is provided via a public git repository.

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arXiv2023

A New Higgs Boson with Electron-Muon Flavor-Violating Couplings

Recently, the CMS Collaboration performed a search on a new resonance decaying to $e^\pm\mu^\mp$ in the mass range of 110 GeV to 160 GeV. The search also hints a possible excess at 146 GeV with a $3.8\sigma~(2.8\sigma)$ of local (global) significance. Motivated by that, we try to interpret the results in the context of the type-III two-Higgs-doublet-model. We find that the excess is only moderately constrained by low-energy lepton-flavor-violation processes, in particular the $\mu\to e \gamma$ decay. We also compare the CMS bounds across the entire search region against constraints of $\mu\to e\gamma$ and $\mu\to e$ conversion in nuclei. Our finding indicates that the collider bounds can be superior to those of low-energy processes for the scalar mass between $110 \text{ GeV}$ and $150 \text{ GeV}$, suggesting the importance of this mass range for future searches.

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arXiv2022

Minimal Zee model for lepton ${g-2}$ and $W$-mass shifts

We present a unique Yukawa structure of the Zee model that can accommodate neutrino oscillation data, solves the muon ${g-2}$ problem, and explains the recent $W$ boson mass measurement. Our Yukawa structure is minimal in the sense that it contains the least possible number of parameters. In this minimal scenario, neutrino masses are quasidegenerate and are compatible with both normal and inverted orderings. The mixing angle $\theta_{23}$ is predicted to lie in the second (first) octant for normal (inverted) ordering. In both cases, the CP violating phase is close to 3$\pi/2$. The minimal texture also predicts a large branching fraction of the heavy neutral Higgs boson into a pair of electron and muon.

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arXiv2022

Marriage between neutrino mass and flavor anomalies

Experimental hints for lepton flavor universality violation in beauty-quark decay both in neutral- and charged-current transitions require an extension of the Standard Model for which scalar leptoquarks (LQs) are the prime candidates. Besides, these same LQs can resolve the long-standing tension in the muon and the recently reported deviation in the electron $g-2$ anomalies. These tantalizing flavor anomalies have discrepancies in the range of $2.5\sigma-4.2\sigma$, indicating that the Standard Model of particle physics may finally be cracking. In this Letter, we propose a resolution to all these anomalies within a unified framework that sheds light on the origin of neutrino mass. In this model, the LQs that address flavor anomalies run through the loops and generate neutrino mass at the two-loop order while satisfying all constraints from collider searches, including those from flavor physics.

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arXiv2022

A flavor-inspired radiative neutrino mass model

One of the most important discoveries in particle physics is the observation of nonzero neutrino masses, which dictates that the Standard Model (SM) is incomplete. Moreover, several pieces of evidence of lepton flavor universality violation (LFUV), gathered in the last few years, hint toward physics beyond the SM. TeV-scale scalar leptoquarks are the leading candidates for explaining these flavor anomalies in semileptonic charged and neutral current B-decays, the muon, and the electron magnetic dipole moments that can also participate in neutrino mass generation. In this work, we hypothesize that neutrino masses and LFUV have a common new physics origin and propose a new two--loop neutrino mass model that has the potential to resolve some of these flavor anomalies via leptoquarks and offers rich phenomenology. After deriving the neutrino mass formula for this newly-proposed model, we perform a detailed numerical analysis focusing on neutrino and charged lepton flavor violation phenomenology, where the latter provides stringent constraints on the Yukawa couplings and leptoquark masses. Finally, present and future bounds on the model's parameter space are scrutinized with exemplified benchmark scenarios.

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arXiv2022

Zee model with quasidegenerate neutrino masses and where to find it

We present a Zee model with a family dependent $Z_2$ symmetry for radiative neutrino masses. Our motivation is to get a model that correctly describes neutrino oscillation phenomena, while at the same time offers definite predictions. The imposed $Z_2$ symmetry greatly reduces the number of free parameters in the model. These parameters are then determined from the neutrino data, from which one can study its outcomes. Our setup only admits quasidegenerate neutrino masses with the sum of neutrino masses between 100 and 130 meV, the effective Majorana mass between 20 and 40 meV, and the effective electron neutrino mass between 48 and 53 meV. The ratio of the vacuum expectation values of the Higgs doublets, $\tbeta$, is found to be $\tbeta\lesssim 0.5$ and $\tbeta\gtrsim 10$. The former is ruled out by lepton flavor violation (LFV) processes, such as $\mu\to e\gamma$ and $\mu\to e$ conversion, which are determined up to two loops. For the latter, these LFV processes are within reach of the next generation of experiments. Moreover, for $\tbeta\gtrsim10$, the couplings of heavy neutral scalars to dimuon are significant. If they are sufficiently light, i.e., $\lesssim200$ GeV, collider search for their decays into muon pair provides a stronger constraint on most parts of the model parameter space than the LFV ones.

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arXiv2020

Collider Constraints on a Dark Matter Interpretation of the XENON1T Excess

In light of the excess in the low-energy electron recoil events reported by XENON1T, many new physics scenarios have been proposed as a possible origin of the excess. One possible explanation is that the excess is a result of a fast moving dark matter (DM), with velocity $v\sim0.05-0.20$ and mass between 1 MeV and 10 GeV, scattering off an electron. Assuming the fast moving DM-electron interaction is mediated by a vector particle, we derive collider constraints on the said DM-electron interaction. The bounds on DM-electron coupling is then used to constrain possible production mechanisms of the fast moving DM. We find that the preferred mass of the vector mediator is relatively light ($\lesssim$ 1 GeV) and the coupling of the vector to the electron is much smaller than the coupling to the fast moving DM.

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arXiv2019

Collider Constraints on Lepton Flavor Violation in the 2HDM

In light of the recent CMS analysis on lepton flavor violating (LFV) heavy Higgs searches and updated bounds on various search channels involving neutral and charged scalars, we provide the updated constraints on the Type-III Two-Higgs-Doublet-Model (2HDM) with a $τ-μ$ LFV. In doing so, we first extend the CMS analysis to cover the mass region below 200 GeV by recasting their data. After obtaining the bounds on the heavy Higgs production in the mass range between 130 GeV and 450 GeV, we analyze the parameter space of the Type-III 2HDM with various scenarios of mass spectrum and heavy Higgs production strengths. We found that in most scenarios, searching for the heavy Higgs in the mass range lower than $2 m_W$ is very important in constraining the parameter space of the Type-III 2HDM. Hence, we suggest for the future analysis that the search window for the LFV heavy Higgs be extended to the lower mass region.

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arXiv2019

Scalar phenomenology in type-II seesaw model

In this work we study the viable parameter space of the scalar sector in the type-II seesaw model. In identifying the allowed parameter space, we employ constraints from low energy precision measurements, theoretical considerations and the 125-GeV Higgs data. These tools prove effective in constraining the model parameter space. Moreover, the triplet also offers a rich collider phenomenology from having additional scalars that have unique collider signatures. We find that direct collider searches for these scalars can further probe various parts of the viable parameter space. These parts can be parametrized by the electroweak scalar triplet vacuum expectation value, the mass splitting of the singly- and doubly-charged scalars, and the doubly-charged Higgs mass. We find that different regions of the viable parameter space give rise to different collider signatures, such as the same-sign dilepton, the same-sign $W$ and the multilepton signatures. By investigating various LEP and LHC measurements, we derive the most updated constraints over the whole range of parameter space of the type-II seesaw model.

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arXiv2013

Constraining Higgs mediated dark matter interactions

We perform an analysis of Higgs portal models of dark matter (DM), where DM is light enough to contribute to invisible Higgs decays. Using effective field theory we show that DM can be a thermal relic only if there are additional light particles present with masses below a few 100 GeV. We give three concrete examples of viable Higgs portal models of light DM: (i) the SM extended by DM scalar along with an electroweak triplet and a singlet, (ii) a Two Higgs Doublet Model of type II with additional scalar DM, (iii) SM with DM and an extra scalar singlet that is lighter than DM. In all three examples the Br(h to invisible) constraint is not too restrictive, because it is governed by different parameters than the relic abundance. Additional light particles can have implications for flavor violation and collider searches.

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arXiv2013

Predictive Model of Radiative Neutrino Masses

We present a simple and predictive model of radiative neutrino masses. It is a special case of the Zee model which introduces two Higgs doublets and a charged singlet. We impose a family-dependent Z_4 symmetry acting on the leptons, which reduces the number of parameters describing neutrino oscillations to four. A variety of predictions follow: The hierarchy of neutrino masses must be inverted; the lightest neutrino mass is extremely small and calculable; one of the neutrino mixing angles is determined in terms of the other two; the phase parameters take CP-conserving values with δ_{CP} = π; and the effective mass in neutrinoless double beta decay lies in a narrow range, m_{ββ} = (17.6 - 18.5) meV. The ratio of vacuum expectation values of the two Higgs doublets, tanβ, is determined to be either 1.9 or 0.19 from neutrino oscillation data. Flavor-conserving and flavor-changing couplings of the Higgs doublets are also determined from neutrino data. The non-standard neutral Higgs bosons, if they are moderately heavy, decay dominantly into μand τwith prescribed branching ratios. Observable rates for the decays μ\to e γand τ\to 3μare predicted if these scalars have masses in the range of 150-500 GeV.

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arXiv2011

Radiative Neutrino Mass Generation through Vector-like Quarks

A new model of radiative neutrino masses generated via two-loop diagrams is proposed involving a charge 2/3 vector-like quark and a doublet of leptoquark scalars. This model predicts one of the neutrinos to be massless and admits both the normal and inverted neutrino mass hierarchies with correlated predictions for l_i \rightarrow l_j + γbranching ratios. New contributions to CP violation in B_s-\bar{B}_s mixing arise in the model through leptoquark box diagrams, which can explain the anomalous dimuon events reported by the DO collaboration. These leptoquarks, with masses below 500 GeV, also provide a natural resolution to the apparent discrepancy in the measured values of the CP violation parameters \sin2βand ε_K.

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arXiv2011

Perturbative unitarity constraints on general W' models and collider implications

We study perturbative unitarity constraints on general W' models by considering the high energy behavior of fermion scattering into gauge bosons. In most cases we survey, a Z' boson with a comparable mass must be present for the theory to be consistent, with fixed couplings to the standard model gauge bosons and fermions. Applying these results to a class of W' models which explains the top quark forward-backward asymmetry observed at the Tevatron, we find that a Z' must exist with a mass below 7-8 TeV and sizable coupling to the light quarks. While such a Z' is strongly constrained by existing experiments, we show that the LHC can explore the entire mass range up to the unitarity limit. We also show how it is possible, by raising the Z' mass consistent with unitarity, to explain the CDF Wjj excess in terms of a light W', without generating an excess in Zjj events.

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arXiv2010

Two-Loop Neutrino Mass Generation through Leptoquarks

We present a new model of radiative neutrino mass generation wherein TeV scale leptoguark scalars induce tiny neutrino masses as two-loop radiative corrections. The neutrino oscillation parameter \sin^2θ_{13} is predicted to be close to the current experimental limit within the model. Rare lepton flavor violating processes mediated by leptoquarks have an interesting pattern: μ-> e γ$ may be suppressed, while μ-> 3 e and μ-e conversion in nuclei are within reach of the next generation experiments. New CP violating contributions to B_s- \bar{B}_s mixing via leptoquark box diagrams are in a range that can explain the recently reported discrepancy with the standard model. D_s^- -> \ell^- νdecays mediated by leptoquarks brings theory and experiment closer, removing an observed 2 sigma anomaly. Muon g-2 receives new positive contributions, which can resolve the discrepancy between theory and experiment. The leptoquarks of the model are accessible to the LHC, and their decay branching ratios probe neutrino oscillation parameters.

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