arXiv subjects

Mario J. Neves

Publications and source records attributed to Mario J. Neves.

9 recordsLinked to original sources

arXiv2025

Updated Bounds on the Minimal Left-Right Symmetric Model from LHC Dilepton Resonance Searches

The Left-Right model is a popular extension of the Standard Model that features three new neutral gauge bosons, $W^{\pm}_R$ and $Z_R$. Collider searches for a Left-Right symmetry are often concentrated on the charged right-handed current, but in this work, we take advantage of the dilepton data at the LHC with center-of-mass energy of 13 TeV and 139 fb$^{-1}$ of integrated luminosity to place lower mass bounds in the $Z_R$ mass based on the $p\,p \rightarrow Z_{R} \rightarrow \ell^{+} \, \ell^{-}$ process. We vary the $SU(2)_R$ gauge coupling from $g_{R}=0.4$ to $g_{R}=1.0$, and impose $M_{Z_R}>4.9$ TeV and $M_{Z_{R}}>6.1$ TeV, respectively. Lastly, we put our findings into perspective with $W_R$ searches at the LHC and show that our limits cover an unexplored region of parameter space, where the right-handed neutrino is heavier than the $W_R$ boson.

hep-ph↗

arXiv2024

Loop Quantum Gravity effects on electromagnetic properties of charged leptons

The efforts in this contribution consist in reassessing a modified Dirac equation that incorporates a $γ^0 γ_5$-Lorentz-symmetry violating (LSV) term induced as a Loop Quantum Gravity (LQG) effect. Originally, this equation has been applied and considered as a good scenario for describing a number of investigations on the flight time of cosmic neutrinos, which suggests that the speed, in vacuum, in connection with the geometry that describes a granular space-time, takes the energy-dependent form, e.g., $v(E) =1 \pm E/E_{\textrm{LSV}}$, with $E_{\textrm{LSV}} \approx 6,5 \times 10^{17}$ GeV for neutrinos. Once LQG provides a viable way to understand this picture consistently, we pursue an analysis of this effective Dirac equation to inspect some of its properties. These include: the derivation of the modified fermionic propagator, attainment of the Gordon decomposition of the vector current with minimal electromagnetic coupling to obtain information on the form factors, examination of the non-relativistic limit of the equation, evaluation of the spin- and velocity-dependent corrections to the Coulomb potential due to LQG effects, and the modified Hamiltonian in the low-relativistic regime. The study of the form factors may open up paths to set up bounds on the LQG parameters from the precision measurements of electromagnetic attributes of the charged leptons, such as their respective electric and magnetic dipole moments.

hep-th↗

arXiv2024

Optical properties and energy propagation in a dielectric medium supporting magnetic current

We examine a dielectric medium supporting a magnetic current in connection with optical properties and energy propagation. The dispersion relations, propagating modes, and some optical effects are examined for isotropic and anisotropic magnetic conductivity tensors, with the latter ones implying nonreciprocal permittivities. The eigenvalues of the effective permittivity are carried out and associated with the optical symmetries (uniaxial, biaxial) and the subjacent crystal systems. Aspects of electromagnetic energy transport for such systems are also discussed, with the group and energy velocities being presented and carried out for all the particular cases addressed. Our results suggest that a dielectric supporting magnetic current breaks the usual equivalence between group velocity and energy velocity that holds in a nonabsorbing medium, while establishing the equivalence between them in an effective absorbing scenario, two unexpected behaviors.

cond-mat.other↗

arXiv2018

Classical electrodynamics and gauge symmetry of the X-boson

In this paper we have obtained several new results concerning the X-boson, which is being considered recently as one of the main candidate of the dark matter particle content. The classical electrodynamics for the X-boson model was explored to understand its propagation in space-time. The field equations (Maxwell-type) and the corresponding wave equations were obtained. They indicate the dispersion relations of both a massive and massless particles. These results can be interpreted as a photon and the X-boson (with a mass of 17 MeV), respectively. The gauge symmetry and gauge transformations were discussed. A full model diagonalization was introduced to obtain a Maxwell sector added up to a Proca sector. After that, we have obtained the retarded Green functions which yield the inhomogeneous solutions of the wave equations for the X-boson fields. We have applied this solution to the charge point motion, and we transformed the potential solution to a quadrature problem. In particular, as an example, we have analyzed the point charge in a straight line uniform motion, where the corresponding electromagnetic charge were calculated.

hep-ph↗

arXiv2018

The protophobic $X$-boson coupled to quantum electrodynamics

The possible origin of an $X$-boson having a mass value around $17 \, \mbox{MeV}$ had motivated us to investigate its interaction with leptons of QED. This new hypothetical particle can possibly be a candidate to describe the so called fifth interaction, in a new physics scenario beyond the Standard Model. The model of the $X$-boson interacting with QED is based on a $U(1) \times U'(1)$ symmetry, where the group $U'(1)$ is attached to the $X$-boson, with a kinetic mixing with the photon. The Higgs sector was revisited to generate the mass for the new boson. Thus, the mass of $17 \, \mbox{MeV}$ fixes a vacuum expected value scale. Thereby, we could estimate the mass of the hidden Higgs field through both the VEV-scale and the Higgs' couplings. A model of QFT was constructed in a renormalizable gauge, and we analyzed its perturbative structure. After that, the radiative correction of the $X$-boson propagator has been calculated at one loop approximation to yield the Yukawa potential correction. The form factors associated with the QED-vertex correction were calculated to confirm electron's anomalous magnetic moment together with the computation of the interaction magnitude. The muon case was discussed. Furthermore, we have introduced a renormalization group scheme to explore the current $X$-boson mass and its coupling constant with the leptons of the Standard Model.

hep-ph↗

arXiv2017

The magnetocaloric effect from the point of view of Tsallis non-extensive thermostatistics

In this work we have analyzed the magnetocaloric effect (MCE) from the Tsallis thermostatistics formalism (TTF) point of view. The problem discussed here is a two level system MCE. We have calculated, both analytically and numerically, the entropy of this system as a function of the Tsallis' parameter (the well known q-parameter) which value depends on the extensivity (q<1) or non-extensivity (q>1) of the system. Since we consider this MCE not depending on the initial conditions, which classify our system as a non-extensive one, we used several greater than one q-parameters to understand the effect of the nonextensive formalism in the entropy as well as the magnetocaloric potential, $ΔS$. We have plotted several curves that shows precisely the behavior of this effect when dealt with non-extensive statistics.

physics.gen-ph↗

arXiv2012

Some aspects of quantum mechanics and field theory in a Lorentz invariant noncommutative space

We obtained the Feynman propagators for a noncommutative (NC) quantum mechanics defined in the recently developed Doplicher-Fredenhagen-Roberts-Amorim (DFRA) NC background that can be considered as an alternative framework for the NC spacetime of the early Universe. The operators formalism was revisited and we applied its properties to obtain a NC transition amplitude representation. Two examples of DFRA's systems were discussed, namely, the NC free particle and NC harmonic oscillator. The spectral representation of the propagator gave us the NC wave function and energy spectrum. We calculated the partition function of the NC harmonic oscillator and the distribution function. Besides, the extension to NC DFRA quantum field theory is straightforward and we used it in a massive scalar field. We had written the scalar action with self-interaction $ϕ^{4}$ using the Weyl-Moyal product to obtain the propagator and vertex of this model needed to perturbation theory. %and the effective action to give rise one-particle-irreducible diagrams. It is important to emphasize from the outset is that the formalism demonstrated here will not be constructed introducing a NC parameter in the system, as usual. It will be generated naturally from an already NC space. In this extra dimensional NC space, we presented also the idea of dimensional reduction to recover commutativity.

hep-th↗

arXiv2012

Path integral formalism in a Lorentz invariant noncommutative space

We introduced a new formulation for the path integral formalism for a noncommutative (NC) quantum mechanics defined in the recently developed Doplicher-Fredenhagen-Roberts-Amorim (DFRA) NC framework that can be considered an alternative framework for the NC spacetime of the early Universe. The operators formalism was revisited and we apply its properties to obtain a NC transition amplitude representation. Two DFRA's systems were discussed, the NC free particle and NC harmonic oscillator. Some temperature concepts in this NC space are also considered. The extension to NC DFRA quantum field theory is straightforward and we apply it to a massive scalar field. We construct the generating functional and the effective action to give rise one-particle-irreducible diagrams. As an example, we set the basis for a $n\;(n\geq 3)$ self-interaction $ϕ^{n}$ to obtain the correction of the perturbation theory to the propagator and vertex of this model. The main concept that we would like to emphasize from the outset is that the formalism demonstrated here will not be constructed introducing a NC parameter in the system, as usual. It will be generated naturally from an already NC space. In this extra dimensional NC space, we presented also the idea of dimensional reduction to recover commutativity.

hep-th↗

arXiv2011

Causality in noncommutative spacetime

In this paper we investigated the causality problem present in the recent work about the Doplicher-Fredenhagen-Roberts-Amorim (DFRA) noncommutative framework which analyzed the complex scalar field. To accomplish this task we provided a brief review of the main ingredients of the problem and we demonstrated precisely that the DFRA algebra obeys the rules of the Canonical Commutation Relations algebra. This fact permitted us to prove the form of the DFRA operators previously constructed in the usual way. After that, we introduced the solution of its Klein-Gordon equation with a source term. Its solution was accomplished through the retarded, advanced and causal Green functions constructed in this noncommutative ten dimensional DFRA spacetime. We believe that this solution constitutes the first step in the elaboration of a quantum field theory using the DFRA formalism where the noncommutative parameter is an ordinary coordinate of the system and therefore has a canonical conjugate momentum.

hep-th↗