Dynamics of charmed and bottomed meson and baryon resonances

Résumé

Particle Physics is currently best described by the Standard Model. Within this framework, the interaction between quarks and gluons is characterized by the theory of Quantum Chromodynamics (QCD). Hadrons can be formed by combining quarks and gluons through strong interaction. However, these interactions happen typically at low energies and, unlike the other theories in the Standard Model, QCD can be only calculated perturbatively at high energies. As a consequence, to describe this non-perturbative regime one has to apply other approaches, like lattice QCD (LQCD), scattering theory, effective theories... In this thesis, special attention will be given to molecular resonances that result from the interaction between two hadrons, which will be described using a combination of non-perturbative resummations and effective theories. In particular we will focus on resonances containing one heavy quark. The thesis is divided into four parts. Part I deals with the mathematical and physical formalism necessary to understand the results. We briefly present begin with chiral perturbation theory ($\chi$PT), local hidden gauge (LHG) formalism and heavy quark spin symmetry (HQSS). Furthermore, we review the concepts of analyticity, unitarity and Riemann sheets of scattering amplitudes and we explain under which conditions triangle loops can give rise to singularities that can be experimentally observed. In Parts II, III and IV we present the results of this dissertation, that were obtained using the techniques outlined previously. In Part II, the behavior of hadrons in the light sector is explored, using the techniques and models presented in the previous chapters, such as the CUA in coupled channels and the study of dynamically generated resonances. In Part III, baryon resonance states with heavy quarks, such as the $\Lambda_{c (b)}^{(*)}, \ \Omega_c^{(*)}$ and $\Xi_{c (b)}^{(*)}$, are studied using the various techniques presented in Parts I and II. In Part~IV we study the effect of triangle singularities in several reactions involving both light and heavy hadrons, making use also of the techniques explored and developed so far in this thesis. Finally, in Part V, a summary of the main results and conclusions obtained in this thesis is given.