Estados excitados em regras de soma da QCD.

Abstract

The QCD Sum Rules approach was proposed by Shifman, Vaishtein and Zakharov (SVZ) in1979 and has been used as a method for extracting useful properties of hadrons having the lowest mass, called as ground states. On the other hand, the most recent experimental results make it clear that the study of the excited states can help to solve many puzzles about the new XYZ mesons structure. In this paper we propose a new method to study the fi rst excited state of the hadrons, in particular we focus our attention on the study of vector mesons and that have been studied previously by SVZ method and they have the tow important observables that are the mass and its decay constant. In principle, our method works as a simple modi cation to the shape of the spectral density of the SVZ method which is written as "pole+continuum" to a new functional form "pole+pole + continuum". We also calculate the meson's masses and their decay constants, where our theoretical values are very close to the experimental values. Moreover, the study of the meson decay constant (2S) provide a very interesting result, because as there is no experimental data available, then our theoretical calculation presents as a prediction of our method.