Light Scalar Meson In QCD Quark Model

There is no doubt that Quantum Chromodynamics is the important theory of the strong interactions. It has been tested quantitatively in hundreds of experiments at high momentum transfer, where asymptotic freedom justifies the use of perturbation theory. QCD is well established, hadron spectroscopy has been relatively inactive, but the absence of exotics remains poorly understood. At present the experimental situation is confused; so is theory. Whether or not the new states are confirmed, the way we look at complicated states of confined quarks and gluons has changed.Glueballs, hybrids and multiquark states are predicted as bound states in models guided by quantum chromodynamics, by QCD sum rules or QCD on a lattice. Experiments have reported evidence for an abundance of meson resonances with 0-+,0++ and 2++ quantum numbers. In particular the sector of scalar mesons is full of surprises theoretically.This thesis is a briefly review of the research on light scalar mesons from the history of exotics to the recent achievements in trial quark models. The concentrations are focused on the qualitative features of models inspired by QCD, which have been seen as the candidates for the exotic mesons disagreeing with simple quark-model expectations. Since many unsolved problems are still remained in the scalar mesons sector, this work would provide a guide to the study of exotics in some inspections.