We calculated bound states of quark-antiquark systems in which at least one of the constituents is a charm or bottom quark. We use a Minkowski-space formalism known as the Covariant Spectator Theory (CST), which, for example, has been successfully applied in exact relativistic calculations of two- and three-nucleon systems based on one-boson-exchange dynamics. It is also used quite extensively...
The nature of the recently discovered $Z_c$ and $Z_b$ structures is intriguing. On the one hand, in the charm sector, the $Z_{c}(3900)^\pm$ and $Z_{c}(4020)^\pm$ were discovered in the $\pi J/\psi$ and $D^\ast\bar D^{(\ast)}+h.c.$ invariant mass spectra. Their nature is puzzling due to their charge, which forces its minimal quark content to be $c\bar c u\bar d$ ($c\bar c d\bar u$)....
Both unpolarized and polarized generalized parton distribution functions (GPDs) of the $\rho$ meson are clculated with the help of a light-front quark model [1-2]. The contributions to the form factors and generalized parton distributions from the valence and nonvalence regimes are discussed and analyzed. Comparing to the available experimental data and Lattice calculation, we find that the...
