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T. Frederico

Publications and source records attributed to T. Frederico.

At least 145 records · Page 8Linked to original sources
arXiv2011

From Running Gluon Mass to Chiral Symmetry Breaking

The gluon propagator is one of the fundamental Green's functions of QCD. It is an essential ingredient in, for example, the modeling of the Schwinger-Dyson equation used to describe hadronic phenomenology. From the Landau gauge gluon propagator, computed with lattice QCD methods, we discuss its interpretation as a massive propagator and measure the gluon mass as a function of the momenta. Special attention is given to the mass at infrared scales. In the last part of the talk, the gluon mass and chiral symmetry breaking are related via an effective model for QCD.

hep-ph↗
arXiv2011

Three-body FSIs in D+ ---> K- pi+ pi+

We stress the importance of three-body final state interactions in $D^+ \to K^- \p^+ \p^+$. The basic building block is the $Kπ$ amplitude with parameters determined by a fit to elastic LASS data. Based on a vector weak vertex, we can describe the $Kπ$ phase production experimental in the elastic region.

hep-ph↗
arXiv2011

A Democratic Gauge Model for Dark/Visible Matter Symmetry

We develop a model for visible matter-dark matter interaction based on the exchange of a weakly interacting massive gauge boson called herein the WIMG. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. We give arguments on particle decays and lifetimes that set a limit on the mass of the WIMG, the gray boson responsible for the very meager communication among these worlds. The 5:1 ratio of dark to visible matter is taken for granted.

hep-ph↗
arXiv2011

Nucleon-nucleon scattering within a multiple subtractive renormalization approach

A methodology to renormalize the nucleon-nucleon interaction, using a recursive multiple subtraction approach to construct the kernel of the scattering equation, is presented. We solve the subtracted scattering equation with the next-leading-order (NLO) and next-to-next-leading-order (NNLO) interactions. The results are presented for all partial waves up to $j=2$, fitted to low-energy experimental data. In our renormalizaton group invariant method, when introducing the NLO and NNLO interactions, the subtraction energy emerges as a renormalization scale and the momentum associated with it comes to be about the QCD scale ($Λ_{QCD}$), irrespectively to the partial wave.

nucl-th↗
arXiv2011

Linking Dynamical Gluon Mass to Chiral Symmetry Breaking via a QCD Low Energy Effective Field Theory

A low energy effective field theory model for QCD with a scalar color octet field is discussed. The model relates the gluon mass, the constituent quark masses and the quark condensate. The gluon mass comes about $\sqrt{N_c}\, Λ_{QCD}$ with the quark condensate being proportional to the gluon mass squared. The model suggests that the restoration of chiral symmetry and the deconfinement transition occur at the same temperature and that, near the transition, the critical exponent for the condensate is twice the gluon mass one. The model also favors the decoupling like solution for the gluon propagator.

hep-ph↗
arXiv2011

Dynamical gap generation in graphene nanoribbons: An effective relativistic field theoretical model

We show that the assumption of a nontrivial zero band gap for a graphene sheet within an effective relativistic field theoretical model description of interacting Dirac electrons on the surface of graphene describes the experimental band gap of graphene nanoribbons for a wide range of widths. The graphene band gap is dynamically generated, corresponding to a nontrivial gapless solution, found in the limit of an infinitely wide graphene ribbon. The nanoribbon band gap is determined by the experimental graphene work function.

cond-mat.mtrl-sci↗
arXiv2011

Vortex and gap generation in gauge models of graphene

Effective quantum field theoretical continuum models for graphene are investigated. The models include a complex scalar field and a vector gauge field. Different gauge theories are considered and their gap patterns for the scalar, vector, and fermion excitations are investigated. Different gauge groups lead to different relations between the gaps, which can be used to experimentally distinguish the gauge theories. In this class of models the fermionic gap is a dynamic quantity. The finite-energy vortex solutions of the gauge models have the flux of the "magnetic field" quantized, making the Bohm-Aharonov effect active even when external electromagnetic fields are absent. The flux comes proportional to the scalar field angular momentum quantum number. The zero modes of the Dirac equation show that the gauge models considered here are compatible with fractionalization.

cond-mat.mtrl-sci↗
arXiv2011

Constraints on two-neutron separation energy in the Borromean $^{22}$C nucleus

The recently extracted matter radius of carbon isotope $^{22}$C allows us to estimate the mean-square distance of a halo neutron with respect to the center-of-mass of this nucleus. By considering this information, we suggest an energy region for an experimental investigation of the unbound $^{21}$C virtual state. Our analysis, in a renormalized zero-ranged three-body model, also indicates that the two-neutron separation energy in $^{22}$C is expected to be found below $\sim$0.4~MeV, where the $^{22}$C is approximated by a Borromean configuration with a pointlike $^{20}$C and two $s$-wave halo neutrons. A virtual-state energy of $^{21}$C close to zero, would make the $^{22}$C, within Borromean nuclei configurations, the most promising candidate to present an excited bound Efimov state or a continuum three-body resonance.

nucl-th↗
arXiv2011

Universality and scaling limit of weakly-bound tetramers

The occurrence of a new limit cycle in few-body physics, expressing a universal scaling function relating the binding energies of two consecutive tetramer states, is revealed, considering a renormalized zero-range two-body interaction applied to four identical bosons. The tetramer energy spectrum is obtained when adding a boson to an Efimov bound state with energy $B_3$ in the unitary limit (for zero two-body binding, or infinite two-body scattering length). Each excited $N-$th tetramer energy $B_4^{(N)}$ is shown to slide along a scaling function as a short-range four-body scale is changed, emerging from the 3+1 threshold for a universal ratio $B_4^ {(N)}/B_3 \simeq 4.6$, which does not depend on $N$. The new scale can also be revealed by a resonance in the atom-trimer recombination process.

physics.atm-clus↗
arXiv2010

Scalar mesons within a dynamical holographic QCD model

We show that the infrared dynamics of string modes dual to $q\bar q$ states within a Dynamical AdS/QCD model of coupled dilaton-gravity background gives the Reggelike spectrum of $f0's$ scalars and higher spin mesons consistent with experimental data. The pion mass and its trajectory were also described with a scale deformation of the metric and a rescaled string mass. The available experimental decay widths of the $S\to PP$ decays provided a complementary check of the proposed classification scheme for$f_0(980)$, $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$ as radial excitations of $f_0(600)$. For $f_0(980)$ we estimated a mixing angle of $\pm 20^o$ with other structures.

hep-ph↗
arXiv2010

Double resonances in Borromean heteronuclear triatomic systems

We investigate the occurrence of Borromean three-body continuum s-wave resonances, in an $ααβ$ system for large negative two-body scattering lengths. The energy and width are determined by a scaling function with arguments given by energy ratios of the two-body virtual state subsystem energies with the shallowest three-body bound state. The Borromean continuum resonances emerging from Efimov states present a peculiar behavior for trapped ultracold atoms near a Feshbach resonance: two resonances with equal energies at different values of the scattering length. The corresponding three-body recombination peaks should merge as the temperature is raised, with one moving towards lower values of the scattering length as the other moves to larger values.

cond-mat.quant-gas↗
arXiv2010

Revisiting the Wu-Yang Monopole: classical solutions and conformal invariance

he Wu-Yang monopole for pure SU(2) Yang-Mills theory is revisited. New classical solutions with finite energy are found for a generalized Wu-Yang configuration. Our method relies on known asymptotic series solutions and explores the conformal invariance of the theory to set the scale for the monopole configurations. Furthermore, by breaking the scale invariance of the pure Yang-Mills theory by a term which simulates the coupling to quark fields, four different monopole configurations with an energy of 2.9 GeV and spatial extent of 1.2 fm, 1.4 fm, 2.4 fm and 2.6 fm are obtained. These configurations may play a role in the transition to the plasma phase.

hep-th↗
arXiv2010

Mesonic Spectrum from a Dynamical Gravity/Gauge model

Within a formulation of a Dynamical AdS/QCD model we calculate the spectrum of light flavored mesons. The background fields of the model correspond to an IR deformed Anti de Sitter metric coupled to a dilaton field. Confinement comes as a consequence of the dilaton dynamics coupled to gravity. Additionally to the Regge-like spectrum of light- scalar, vector and higher spin mesons, we obtain the decay width of scalar mesons into two pions.

hep-ph↗
arXiv2010

Scalar Spectrum from a Dynamical Gravity/Gauge model

We show that a Dynamical AdS/QCD model is able to reproduce the linear Regge trajectories for the light-flavor sector of mesons with high spin and also for the scalar and pseudoscalar ones. In addition the model has confinement by the Wilson loop criteria and a mass gap. We also calculate the decay amplitude of scalars into two pion in good agreement to the available experimental data.

hep-ph↗
arXiv2010

Light-Front Model of Transition Form-Factors in Heavy Meson Decay

Electroweak transition form factors of heavy meson decays are important ingredients in the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements from experimental data. In this work, within a light-front framework, we calculate electroweak transition form factor for the semileptonic decay of $D$ mesons into a pion or a kaon. The model results underestimate in both cases the new data of CLEO for the larger momentum transfers accessible in the experiment. We discuss possible reasons for that in order to improve the model.

hep-ph↗
arXiv2010

Light-front projections of the Bethe-Salpeter amplitude and the 4D electromagnetic current for an interacting two-fermion system

A recent approach for constructing an exact 3D reduction of the 4D matrix elements of the electromagnetic current for an interacting two-fermion system, is briefly reviewed. The properties of the obtained 3D current, like the fulfillment of the Ward-Takashi Identity and its Fock decomposition, will be illustrated in relation with future applications to few-nucleon systems.

hep-ph↗
arXiv2010

A covariant investigation of Neutral Vector Mesons: dynamical properties and electromagnetic decay widths

A simple, but fully-covariant model for describing neutral Vector Mesons, in both light and heavy sectors, is briefly illustrated. The main ingredients of our relativistic constituent model are i) an Ansatz for the Bethe-Salpeter vertex for Vector Mesons, and ii) a Mandelstam-like formula for the electromagnetic decay widths. The free parameters of our approach are fixed through a comparison with the valence transverse-momentum distribution, $n(k_\perp)$, obtained within phenomenological Light-Front Hamiltonian Dynamics models reproducing the mass spectra. Preliminary results for the transverse-momentum distributions, the parton distribution and the electromagnetic decay constants are shown.

hep-ph↗