arXiv subjects

M. J. Neves

Publications and source records attributed to M. J. Neves.

51 records · Page 3Linked to original sources

arXiv2018

A Unified Hidden-Sector-Electroweak Model, Paraphotons and the X-Boson

Our contribution sets out to investigate the phenomenology of a gauge model based on an $SU_{L}(2) \times U_{R}(1)_{J} \times U(1)_{K}$-symmetry group. The model can accommodate in its distinct phases - by virtue of different symmetry-breaking patterns - a candidate to a heavy $Z'$-boson at the TeV-scale and the recently discussed $17 \, \mbox{MeV}$ X-boson that may bring about a new physics at the $\mbox{MeV}$-scale. Furthermore, the para-photon of the dark matter sector and the candidate to the so-called dark photon can also be described in the scenario we are endeavoring to set up in this paper. In the $Z'$-scenario, the extended Higgs sector introduces a heavy scalar whose mass lies in the region $1.2-3.7 \, \mbox{TeV}$, while that the lower energy scale scenario presents a light scalar with mass in the interval $1.9-19 \, \mbox{GeV}$. The fermionic sector includes an exotic candidate to dark matter that mixes with the right-neutrino component in the Higgs sector, so that the whole field content yields the cancellation of the U(1)-anomaly. The masses are fixed according to the particular way the symmetry breaking takes place. In view of the possible symmetry breakdown patterns, we study the phenomenological implications in both scenarios of high- and low-energy scales. As examples, we consider the scattering of Standard Model matter into dark sector constituents intermediated by the $Z'$-boson in the $\mbox{TeV}$-scale, and the corresponding scattering intermediated by a lightest boson in the lower scale physics. Furthermore, we obtain the magnetic dipole momentum (MDM) of the exotic fermion and the transition MDM due to the mixing with the right-neutrino.

hep-ph↗

arXiv2017

TeV- and MeV-physics out of an $SU_{L}(2)\times U_{R}(1)_{J} \times U(1)_{K}$ model

The standard electroweak interaction is here re-assessed to accommodate two different situations in Particle Physics. The first one is a $Z'$-model at the TeV-scale physics. The second one tackles the recent discussion of a possible fifth force mediated by a $17$-MeV X-boson associated with an electron-positron emission in the transition of an excited 8-Beryllium to its ground state. The anomaly-free model that provides these two scenarios is based on an $SU_{L}(2) \times U_{R}(1)_{J} \times U(1)_{K}$-symmetry. It yields a new massive neutral boson, an exotic massive neutral fermion, right-neutrinos and an additional neutral Higgs particle, which stems from a supplementary Higgs field, introduced along with the usual Higgs doublet responsible for the electroweak breaking and the masses of $W^{\pm}$ and $Z^{0}$. Yukawa interactions of the two scalars generate the masses of the Standard Model leptons, neutrinos and a new exotic fermion of the model. The vacuum expectation values of the Higgses fix up two independent energy scales. One of them is the well-confirmed electroweak scale, $246 \, \mbox{GeV}$, whereas the other one is set up by adopting an experimental estimate for the $Z'$-mass.

hep-ph↗

arXiv2016

A non-abelian model $SU(N) \times SU(N)$

A composite non-abelian model $SU(N) \times SU(N)$ is proposed as possible extension of the Yang-Mills symmetry. We obtain the corresponding gauge symmetry of the model and the most general lagrangian invariant by $SU(N) \times SU(N)$. The corresponding Feynman rules of the model are studied. Propagators and vertices are derived in the momentum space. As physical application, instead of considering the color symmetry $SU_{c}(3)$ for $QCD$ , we substitute it by the combination $SU_{c}(3) \times SU_{c}(3)$. It yields a possibility to go beyond $QCD$ symmetry in the sense that quarks are preserved with three colors. This extension provides composite quarks in triplets and sextets multiplets accomplished with the usual massless gluons plus massive gluons. We present a power counting analysis that satisfies the renormalization conditions as well as one studies the structure of radiative corrections to one loop approximation. Unitary condition is verified at tree level. Tachyons are avoided. For end, one extracts a BRST symmetry from lagrangian and Slavnov-Taylor identities.

hep-th↗

arXiv2016

The Strong Interaction Model in DFR noncommutative space-time

The Doplicher-Fredenhagen-Roberts (DFR) framework for noncommutative (NC) space-times is considered as an alternative approach to describe the physics of quantum gravity. In this formalism, the NC parameter, {\it i.e.} $θ^{μν}$, is promoted to a coordinate of a new extended space-time. Consequently, we can construct a Field Theory in a space-time with spatial extra-dimensions. This new coordinate has a canonical momentum associated, where the effects of a new physics point of view can emerge in the fields propagation along the extra-dimension. In this paper we have introduced the gauge invariance in the DFR NC space-time by the composite symmetry $U^{\star}(N)\times U^{\star}(N)$. We have constructed the non-Abelian gauge symmetry based on DFR formalism, and we analyzed the consequences of this symmetry in the presence of such extra-dimensions. The gauge symmetry in this DFR scenario can reveal new gauge fields attached to $θ$-extra-dimension. As an application, we have accomplished the unification of Strong Interaction with the electromagnetism and a Higgs model to give masses to the NC bosons. We have estimated their masses by using some experimental constraints of QCD.

hep-th↗

arXiv2016

The standard electroweak model in the noncommutative $DFR$ space-time

The noncommutative (NC) framework elaborated by Doplicher, Fredenhagen and Roberts (DFR) has a Lorentz invariant spacetime structure in order to be considered as a candidate to understand the physics of the early Universe. In DFR formalism the NC parameter ($θ^{μν}$) is a coordinate operator in an extended Hilbert space and it has a conjugate momentum. Since $x$ and $θ^{μν}$ are independent coordinates, the Weyl-Moyal (WM) product can be used in this framework. With these elements, in this work, we have constructed the standard electroweak model. To accomplish this task we have begun with the WM-product basis group of symmetry. After that we have introduced the spontaneous symmetry breaking and the hypercharge in DFR framework. The electroweak symmetry breaking was analyzed and the masses of the new bosons were computed. Finally, the gauge symmetry and gauge transformations were discussed.

hep-th↗

arXiv2016

Quantum electrodynamics and the electron self-energy in a deformed space with a minimal length scale

The main motivation to study models in the presence of a minimal length is to obtain a quantum field theory free of the divergences. In this way, in this paper, we have constructed a new framework for quantum electrodynamics embedded in a minimal length scale background. New operators are introduced and the Green function method was used for the solution of the field equations, i.e., the Maxwell, Klein-Gordon and Dirac equations. We have analyzed specifically the scalar field and its one loop propagator. The mass of the scalar field regularized by the minimal length was obtained. The QED Lagrangian containing a minimal length was also constructed and the divergences were analyzed. The electron and photon propagators, and the electron self-energy at one loop as a function of the minimal length was also obtained.

hep-th↗

arXiv2015

Spontaneous symmetry breaking and masses numerical results in DFR noncommutative space-time

With the elements of the Doplicher, Fredenhagen and Roberts (DFR) noncommutative formalism, we have constructed the standard electroweak model. To accomplish this task we have begun with the WM-product basis group of symmetry. We have introduced the spontaneous symmetry breaking and the hypercharge in DFR framework. The electroweak symmetry breaking was analyzed and the masses of the new bosons were computed.

hep-th↗

arXiv2015

A 3-form Gauge Potential in 5D in connection with a Possible Dark Sector of 4D-Electrodynamics

We here propose a 5-dimensional {\bf Abelian gauge} model based on the mixing between a $U(1)$ potential and an Abelian 3-form field by means of a topological mass term. An extended covariant derivative is introduced to minimally couple a Dirac field to the $U(1)$ potential, while this same covariant derivative non-minimally couples the 3-form field to the charged fermion. A number of properties are discussed in 5D; in particular, the appearance of a topological fermionic current. A 4-dimensional reduced version of the model is investigated and, { \bf in addition to the $U(1)$ electric- and magnetic-sort of fields,} there emerges an extra set of electric- and magnetic-like fields which contribute a negative pressure and may be identified as a possible fraction of dark energy. The role of the topological fermionic current is also contemplated upon dimensional reduction from 5D to 4D. Other issues we present in 4 space-time dimensions are the emergence {\bf of a pseudo-scalar massive particle,} an extra massive neutral gauge boson,{\bf which we interpret as a kind of paraphoton}, and the calculation of spin- and velocity-dependent interparticle potentials associated to the exchange of the intermediate bosonic fields of the model.

hep-th↗

arXiv2015

Probing features of the Lee-Wick quantum electrodynamics

In this paper we discuss some aspects concerning the electromagnetic sector of the abelian Lee-Wick (LW) quantum electrodynamics (QED). Using the Dirac's theory of constrained systems, the higher-order canonical quantization of the LW electromagnetism is performed. A quantum bound on the LW heavy mass is also estimated using the best known measurement of the anomalous magnetic moment of the electron. Finally it is shown that magnetic monopoles can coexist peacefully in the LW scenario.

hep-th↗

arXiv2015

The Yang-Mills gauge theory in DFR noncommutative space-time

The Doplicher-Fredenhagen-Roberts (DFR) framework for noncommutative (NC) space-times is considered as an alternative approach to describe the physics of quantum gravity, for instance. In this formalism, the NC parameter, {\it i.e.} $θ^{μν}$, is promoted to a coordinate of a new extended space-time. Consequently, we have a field theory in a space-time with spatial extra-dimensions. This new coordinate has a canonical momentum associated, where the effects of a new physics can emerge in the fields propagation along the extra-dimension. In this paper we introduce the gauge invariance in the DFR NC space-time. We present the non-Abelian gauge symmetry in DFR formalism, and the consequences of this symmetry in the presence of such extra-dimension. The gauge symmetry in this DFR scenario can reveal new fields attached to $θ$-extra-dimension. We obtain the propagation of these gauge fields in terms of canonical momentum associated with $θ$-coordinate.

hep-th↗

arXiv2015

New remarks on DFR noncommutative phase-space

The so-called canonical noncommutativity is based on a constant noncommutative parameter ($θ$). However, this formalism breaks Lorentz invariance and one way to recover it is to define the NC parameter as a variable, an extra coordinate of the system. One approach that uses the variable $θ$ was developed by Doplicher, Fredenhagen and Roberts (DFR) and hence, their phase-space is formed by $(x,p,θ)$ with extra-dimensions. In this work we have demonstrated precisely that this phase-space is incomplete because the variable $θ$ requires an associated momentum and the so-called DFR phase-space is in fact formed by $(x, p, θ, π)$, where $π$ is an useful object. One of the models used here to demonstrate this fact brought other interesting results. We have used this complete phase-space to explain some undefined results in the $θ$-variable literature. Finally, we have shown the importance of this DFR-momentum since with it we could fill the gap that exist in $θ$-variable results. In other words, we have computed the field commutation relations of a QFT in this DFR phase-space. The results obtained here match exactly with the postulated (not demonstrated) values that dwell in the DFR literature.

hep-th↗

arXiv2013

Self-quartic interaction for a scalar field in an extended DFR noncommutative spacetime

The framework Doplicher-Fredenhagen-Roberts (DFR) of a noncommutative (NC) space-time is considered as a alternative approach to study the NC space-time of the early Universe. In this formalism, the parameter of noncommutative $θ^{μν}$ is promoted to a coordinate of the space-time, and consequently, we are describing a field theory in a space-time with extra-dimension. Consequently, there is a canonical momentum associated to this new coordinate in which the effects of a new physics can emerge in the propagation of the fields along the extra-dimension. The Fourier space of this framework is automatically extended by the addition of new momenta components. 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. When the components of the new momentum are zero, the DFR approach is reduced to the usual NC case, in which $θ^{μν}$ is a antisymmetric constant matrix. We study a scalar field action with self-quartic interaction $ϕ^{4}\star$ defined in the DFR NC spacetime, obtaining the Feynman rules in the Fourier space for the scalar propagator and vertex of the model. With these rules we are able to build out the radiative corrections to one loop order for the model propagator. The influence of the NC scale, as well as the propagation of the field in the extra-dimension, are analyzed in the ultraviolet divergences scenario. We investigate the actual possibility if this $θ^{μν}$ conjugate momentum has the property of healing the mixing IR/UV divergences that emerges in this recently new NC spacetime quantum field theory.

hep-th↗

arXiv2010

Past and future blurring at fundamental length scale

We obtain the $κ$-deformed versions of the retarded and advanced Green functions and show that their causality properties are blurred in a time interval of the order of a length parameter $q=1/(2κ)$. The functions also indicate a smearing of the light cone. These results favor the interpretation of $q$ as a fundamental length scale below which the concept of a point in spacetime should be substituted by the concept of a fuzzy region of radius $q$, as proposed long ago by Heisenberg.

hep-th↗

arXiv2008

Primitively divergent diagrams in $κ$-deformed scalar field with quartic self-interaction

We obtain the primitively divergent diagrams in $κ$-deformed scalar field in four-dimensional spacetime with quartic self-interaction in order to investigate the effect of the fundamental length $q=1/(2κ)$ on such diagrams. Thanks to $κ$-deformation, we find that the dimensionally regularized forms of the diagrams lead to finite results in the limit of space-time dimension four. The effect of the deformation appears as a displacement of the poles in the complex plane.

hep-th↗

arXiv2007

Relativistic Green functions in a plane wave gravitational background

We consider a massive relativistic particle in the background of a gravitational plane wave. The corresponding Green functions for both spinless and spin 1/2 cases, previously computed by A. Barducci and R. Giachetti \cite{Barducci3}, are reobtained here by alternative methods, as for example, the Fock-Schwinger proper-time method and the algebraic method. In analogy to the electromagnetic case, we show that for a gravitational plane wave background a semiclassical approach is also sufficient to provide the exact result, though the lagrangian involved is far from being a quadratic one.

hep-th↗