Related papers: g-coupling (g_B*Bpi,g_D*Dpi); A quark model with D…
Radiative decays $D^*_{(s)}\to D_{(s)}\gamma$ are revisited in light of new experimental data from the \textit{BABAR} and BESIII collaborations. The radiative couplings $g_{D^*D\gamma}$ encoding nonperturbative QCD effects are calculated in…
We study the stability of Dirac semimetals with $N$ nodes in three spatial dimensions against strong $1/r$ Coulomb interactions. We particularly study the cases of $N=4$ and $N=16$, where the $N=4$ Dirac semimetal is described by the…
We discuss some problems with the large Nc approximation for nucleons which arise if the axial coupling of the nucleon to pions is large, g_A \sim Nc. While g_A \sim Nc in non-relativistic quark and Skyrme models, it has been suggested that…
We study a supersymmetric scenario with a quasi exact R-symmetry in light of the discovery of a Higgs resonance with a mass of 125 GeV. In such a framework, the additional adjoint superfields, needed to give Dirac masses to the gauginos,…
A quark model is applied to the spectrum of baryons containing heavy quarks. The model gives masses for the known heavy baryons that are in agreement with experiment, but for the doubly-charmed baryon Cascade_{cc}, the model prediction is…
In this work, we analyze the strong vertices $\Sigma_{c}\Delta D^{*}$ and $\Sigma_{b}\Delta B^{*}$ using the three-point QCD sum rules under the tensor structures $i\epsilon^{\rho\tau\alpha\beta}p_{\alpha}p'_{\beta}$, $p^{\rho}p'^{\tau}$…
The quark-meson coupling (QMC) model incorporates quark degrees of freedom into the relativistic mean-field (RMF) framework, distinguishing it from traditional quantum hadrodynamics (QHD), which treats nucleons as point-like particles. In…
We study a Dirac fermion model with a random vector field, especially paying attention to a strong disorder regime. Applying the bosonization techniques, we first derive an equivalent sine-Gordon model, and next average over the random…
We study SU(3)$_L\timesSU(3)_R$ chiral quark model of mesons up to the next to leading order of $1/N_c$ expansion. Composite vector and axial-vector mesons resonances are introduced via non-linear realization of chiral SU(3) and vector…
The strong coupling constants are basic quantities that carry information of the strong interactions among the baryon and meson multiplets as well as information on the natures and internal structures of the involved hadrons. These…
Motivated by the recent CMS observation of a near-threshold enhancement in top quark pair production, we investigate a novel class of hadronic systems containing a single top quark: the topped mesons ($t\bar{q}$, with $\bar q = \bar u, \bar…
We study two-dimensional massless Dirac fermions at neutrality, coupled to bosonic modes through a Yukawa interaction. We then examine the intriguing possibility that such a system, devoid of carriers at zero temperature, might nevertheless…
The Fixed Point Dirac Operator and Chirally Improved Fermions both use large numbers of gauge paths and the full Dirac structure to approximate a solution of the Ginsparg-Wilson equation. After a brief review of the two approaches we…
We study a chiral quark model of $\pi$, $\sigma$, $\rho$, and $a_1$ mesons in the large-$N_c$ limit. We show that the quadratic $a_1-\pi$ mixing can be set to zero at zero momentum, thus protecting the $g_{\sigma\pi\pi}$ and…
We propose a model for Quantum Chromodynamics, obtained by ignoring the angular dependence of the gluon fields, which could qualitatively describe systems containing one heavy quark. This leads to a two dimensional gauge theory which has…
The Dirac equation for a massive spin-1/2 field in a central potential V in three dimensions is studied without fixing a priori the functional form of V. The second-order equations for the radial parts of the spinor wave function are shown…
The Dirac structure of confinement is shown to be of timelike-vector nature in the heavy quark limit of QCD. This stands in contradiction with the phenomenological success of the Dirac scalar confining potential. A resolution is achieved…
We compute masses of positive parity spin-$1/2$ and $3/2$ baryons composed of $u$, $d$, $s$, $c$ and $b$ quarks in a quark-diaquark picture. The mathematical foundation for this analysis is implemented through a symmetry-preserving…
The Goldberger--Treiman relation for heavy--light systems is derived in the context of a quark model. As a paradigmatic example, the case of ${\bar D}\to {\bar D}' \pi $ is studied in detail. The fundamental role played by the pion…
We extract an effective strong coupling constant using low-Q^2 data and sum rules. Its behavior is established over the full Q^2-range and is compared to calculations based on lattice QCD, Schwinger-Dyson equations and a quark model.…