Estudo da largura de estados exóticos do Charmonium usando as regras de soma da QCD

Abstract

In this thesis, we discuss in details the QCD Sum Rules (QCDSR) technique and its application to the study of hadronic systems situated in the charmonium mass region. In particular, we applied QCDSR to calculate hadronic properties such as the mass, the coupling contants as well as the total decay width of the Y (4260), Y (3940) and Z c (3900) charmoniumlike states. We have also predicted the decay width of the strange partner of the Z c (3900), called Z cs(3970), to be searched in future experiments. In order to describe these states, we used exotic models. For Y (4260) and Y (3940) states we used mixed charmonium-tetraquarks interpolating currents. For the charged states we used tetraquark currents. As a result of the application of QCDSR to these systems, we obtained masses and decay widths in good agreement with the experimental values measured by BESIII, Babar, and CLEO-c collaborations. Therefore, the currents we used within QCDSR approach provide a good interpretation for these states. Furthermore, applying effective field theories techniques, we also investigated the charged states Z c (4025) and Z c (3900), in addition to Z + b (10610) and Z + b (10650) in the bottom sector. Specifically, we used hidden local symmetry Lagrangians (HGS) together with heavy quark spin symmetry rules (HQSS) in order to study the interactions DD∗, D∗D∗, BB∗ and B∗B∗ by means of the heavy vector exchange and also from the exchange of two pions, interacting and noninteracting among themselves. We obtained the potencial for each interaction, then we used them as a kernel of the Bethe-Salpeter equation in order to look for poles in the T -matrix. Our aim was to relate these poles with the charmoniumlike states of interest. As a result, in the charm sector, we obtained bound states whoses masses and widths are in a good agreement with the charged states we have studied. With respect to the bottom sector, we have found a loosely bound state very close to the BB∗ threshold with mass and width compatible with the structure Zb(10610) observed by Belle colaboration. We have obtained a cusp in the B∗B∗ threshold very close to the mass of the Z b (10650) state. Palavras-Chave: QCD Sum Rules, Hadron Physics, Mesons, Charmonium, Exotic States, Mass, Width.