arXiv subjects

F. Ramírez-Zavaleta

Publications and source records attributed to F. Ramírez-Zavaleta.

10 recordsLinked to original sources

arXiv2026

Production of the top partner $T$ of the Bestest Little Higgs Model at the future muon collider

In this work, we evaluate the decay widths and branching ratios of the heavy top partner $T$, and perform a comprehensive phenomenological study of its pair and associated production at a muon collider within the framework of the Bestest Little Higgs Model (BLHM). The BLHM provides an attractive and natural mechanism for addressing the fine-tuning problem in the Standard Model (SM) of particle physics. In our study of the top partner $T$, we consider the production processes $μ^{+} μ^{-} \to (γ, Z, Z', h, H) \to T \bar{T}$ and $μ^{+} μ^{-} \to (γ, Z, Z', h, H)\to \bar{t}T+ t \bar{T}$, and we explore different center-of-mass energies of the muon collider to perform our numerical analysis of the production cross sections for the processes of interest. Our results show that pair production is the most promising channel for probing the top partner of the BLHM at a future muon collider.

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arXiv2026

Lepton-flavor violating decays induced by Lorentz violation in the Yukawa sector of the Standard Model Extension

Tree-level lepton-flavor-violating decays induced by Lorentz-violating effects within the Yukawa sector of the Standard Model Extension are studied. These new physics effects are parameterized by the $(Y_{f})_{μν}^{AB}$ tensor, with $μ$ and $ν$ denoting Lorentz indices and $A$, $B$ being indices in the flavor space. Since this tensor is antisymmetric under the interchange of Lorentz indices, in analogy with the electromagnetic tensor $F_{μν}$, $(Y_{f})_{μν}^{AB}$ can be expressed in terms of six components associated with two complex three-vectors denoted by $\mathbf{e}_l^{AB}$ and $\mathbf{b}_l^{AB}$. On the assumption that these three-vectors are pure real or pure imaginary and mutually orthogonal, constraints on their magnitudes via experimental bounds on lepton-flavor-violating processes $\mathrm{Br}(l_B\rightarrow γl_A)$ and $\mathrm{Br}(l_B\rightarrow l_A l_C \bar{l}_C)$ are estimated. Thus, the $l_B\rightarrow γl_A$ decay provides the following upper bounds: $\lvert \mathbf{e}_l^{μτ} \lvert < 1.51\times 10^{-11}$ , $\lvert \mathbf{e}_l^{eτ} \lvert < 1.34 \times 10^{-11}$, $\lvert \mathbf{e}_l^{eμ} \lvert < 3.65 \times 10^{-18}$, $\lvert \mathbf{b}_l^{μτ} \lvert < 1.95\times 10^{-11}$, $\lvert \mathbf{b}_l^{eτ} \lvert <1.73\times 10^{-11}$, $\lvert \mathbf{b}_l^{eμ} \lvert < 4.71\times 10^{-18}$. Conversely, by assuming that the Lorentz-violating parameters are purely real, for the $l_B\rightarrow l_A l_C \bar{l}_C$ process it is found that $\lvert \mathbf{e}_l^{μτ}\lvert< 3.05 \times 10^{-12}$ and $\lvert \mathbf{b}_l^{μτ}\lvert< 4.31 \times 10^{-12}$. These results offer more restrictive bounds than those previously reported in the literature.

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arXiv2025

Dipolar electroweak properties of Dirac massive neutrinos

Electroweak properties of Dirac neutrinos within the context of the Minimally Extended Standard Model are explored. In particular, the dipolar form factors that result from the radiative correction, at one-loop level, of the $ Zν\barν$ coupling are identified. The calculation is carried out in the covariant general gauge $R_ξ$. The results are shown to be independent of the gauge parameter. The outcome numerical evaluation establishes that the neutrino weak-magnetic dipole moment is of the same order of magnitude as the known prediction of the neutrino magnetic dipole moment.

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arXiv2024

Probing the heavy Higgs boson production and decay $H_0$ of the Bestest Little Higgs Model at the LHC and the FCC-hh

In the Bestest Little Higgs Model (BLHM) scenario, we analyze the branching ratios and production cross-section of the heavy Higgs boson $H_0$. The analysis is performed at the tree level and the one-loop level. In addition, we present results of the possible production of the heavy Higgs boson $H_0$ via gluon fusion for the center-of-mass energies and the integrated luminosities of the LHC, HE-LHC, HL-LHC, and FCC-hh. Our results show a very optimistic scenario for studying the $H_0$ scalar predicted by the BLHM and for the energies and luminosities of current and future hadron colliders.

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arXiv2022

Research on the electromagnetic and weak dipole moments of the tau-lepton at the Bestest Little Higgs Model

In this paper, using the Bestest Little Higgs Model (BLHM) we calculate at the one-loop level the contributions to the Anomalous Magnetic Dipole Moment (AMDM) and Anomalous Weak Magnetic Dipole Moment (AWMDM) of the tau-lepton. The implications from this model are study, emphasizing the contributions of the new physics induced by the new scalar and vector bosons of the BLHM: $S_i=H_0, A_0, ϕ^{0}, η^{0}, σ, H^{\pm}, ϕ^{\pm}, η^{\pm}$, and $V_i=Z', W'$, because these quantify the new physics. With these new contributions we estimated bounds on both the real and imaginary parts of the AMDM and AWMDM of the tau-lepton. Our study complements other one-loop level research performed on models beyond the Standard Model.

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arXiv2021

Chromomagnetic dipole moment of the top quark in the Bestest Little Higgs model

We calculate the chromomagnetic dipole moment of the top quark, $\hatμ_t$, in the context of the Bestest Little Higgs model. This extension of the Standard Model aims to solve the hierarchy problem without fine tuning, by introducing one-loop corrections to the Higgs boson mass through heavy top quark partners and heavy gauge bosons. We found that the largest resulting value for the chromomagnetic is $\hatμ_t\sim 10^{-5}$ and the lowest is around $10^{-6}$, mainly due to the Higgs boson of the Standard Model, which couples to both the top quark of the Standard Model and its heavy partners. Also, we present a wide variety of new Feynman rules involved in our calculation.

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arXiv2021

Revisiting the top quark chromomagnetic dipole moment in the SM

We revisit the anomalous chromomagnetic dipole moment in the Standard Model and show that its triple gluon vertex contribution, with the on-shell gluon ($q^2=0$), generates an infrared divergent pole. Consequently, the chromomagnetic dipole should not be perturbatively evaluated at $q^2=0$. Focusing on this top quark anomaly, denoted as $\hatμ_t(q^2)$, we compute it with the off-shell gluon with a large momentum transfer, just as the $α_s(m_Z^2)$ convention scale, for both spacelike $q^2=-m_Z^2$ and timelike $q^2=m_Z^2$ cases. We found that $\hatμ_t(-m_Z^2)$ $=$ $-0.0224$ $-0.000925i$ and $\hatμ_t(m_Z^2)$ $=$ $-0.0133$ $-0.0267i$. Our $\mathrm{Re}\thinspace\hatμ_t(-m_Z^2)$ matches well with the current experimental value $\hatμ_t^\mathrm{Exp}=-0.024_{-0.009}^{+0.013}(\mathrm{stat})_{-0.011}^{+0.016}(\mathrm{syst})$, and the $\mathrm{Im}\thinspace\hatμ_t(-m_Z^2)$ part is induced by flavour changing charged currents.

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arXiv2020

Revisiting the rare $H\to q_iq_j$ decays in the Standard Model

We revisit the rare decays of the Higgs boson to two different quarks in the Standard Model, which arise at the one-loop level. We perform Taylor series expansions to the complete form factors of the decay amplitudes, according to their different mass hierarchies, this allow us to take full advantage of the GIM mechanism to eliminate spurious contributions and retain those that truly contribute. We found that Br$(H\to uc)$=$5.00\times10^{-20}$, Br$(H\to ds)$=$1.19\times10^{-11}$, Br$(H\to db)$=$5.16\times10^{-9}$ and Br$(H\to sb)$=$1.15\times10^{-7}$. Our predictions for the $H\to uc,ds$ decays disagree with previous results in the literature.

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arXiv2017

Heavy neutral pseudoscalar decays into gauge bosons in the Littlest Higgs Model

We study two-body decays of a new neutral pseudoscalar into gauge bosons within the context of the Littlest Higgs model. Concretely, the $Φ^P \to WW, VV, gg$ processes induced at the one-loop level, with $V=γ, Z$, are considered. Since the branching ratios of the $Φ^P \to VV$ decays result very suppressed, only the $Φ^P \to WW, gg$ processes are thoroughly studied. The branching ratios for the $Φ^P \to gg$ and $Φ^P \to WW$ decays are of the order of $10^{-4}$ and $10^{-6}$, respectively, for $f$ around 2 TeV, which represents the global symmetry breaking scale of the theory. The production cross section of the $Φ^P$ boson via gluon fusion at LHC is estimated.

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arXiv2015

The $Z_H \to γH$ decay in the Littlest Higgs Model

We present the calculation of the $Z_H \to γH$ decay in the context of the Littlest Higgs model at one-loop level. Our calculations include the contributions of fermions, scalars and gauge bosons in accordance with the most recent experimental constraints on the parameters space of the model. We find branching ratios of the order of $10^{-5}$ for the energy scale $f=2,3,4$ TeV on the $0.1<c<0.9$ region. In order to provide a complementary study we calculated the production cross section of the $Z_H$ boson in $pp$ collisions at Large Hadron Collider with a center of mass energy of 14 TeV. By using the integrated luminosity projected for the Large Hadron Collider in the last stage of operation, we estimated the number of events for this process. Moreover, we analyze the SM background for the Higgs-photon associated production and found that the $pp\to Z_H X \to γH$ production is above the SM background.

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