Dynamical Studies Of The New Hadronic States

Quantum Chromodynamics is a theory describing the strong interaction, which has three features, i.e. asymptotic freedom, chiral symmetry and quark confinement. In the high energy region of QCD, the effective coupling is very small, so the perturbative theory still works, and the corresponding physical phenomenon are very well studied. However, in the low energy region, the running coupling constant becomes larger, so that the perturbative theory does not work. Because of this, the physics in this case has not been understood well. So the methods of phenomenology seem too much important, which include potential model, quark pair creation model, the effective theory on the hadron level, etc.In the past several decades, high energy physical experiments including Belle, BES, Babar, CDF, D0, CLEO, LHC, and so on, have made a great effort. The corresponding processes of the measurement covers B decay, the initial radiation, e+e-annihilation, γγ fusion. In these experiments, plenty of new hadronic states have been observed, for example, charmed mesons, light resonances, charmonium/bottomonium-like states, and so on.In the third chapter, we studied the spectrum of molecular states by using one-boson-exchange model. In this framework, constituent mesons interact with each other by exchanging light mesons. The long range interaction is related to the pseudoscalar meson exchange, while the short and middle range exchange the vector meson exchange. Since the molecular states we consider are all loosely bound states, the long range interaction seems more important. So we present the one pion exchange results as well. For D(*)D(*), B(*)B(*)D(*)B(*) systems, when considering the mixture of S wave and D wave, we obtain some bound state solutions. For D(*)D(*),B(*)B(*),D(*)B(*) systems, we specially consider the coupled channel effect in flavor space as well as the S and D wave mixing, and we also predict some possibly existing hadronic molecules. In addition, the newly observed Zb(10610) and Zb(10650) by Belle Collaboration have been discussed. They can be naturally explained as B(*)B(*) molecular states; Similarly,Zc(4025) firstly reported by BES-Ⅲ may also be a candidate molecular state.