The Study Of The Z’_c Radioative Decays In The Scenario Of Hadronic Molecules

In this thesis, we focus on the study of hadronic molecular exotics containing heavy quarks. During the last decade, the progress on experimental facilities has led to ob-servations of many candidates for hadronic exotics, in experiment, namely the so-called "XYZ states", which cannot be accommodated by the conventional quark model. To ex-plain and understand the properties and structures of these states, a lot of scenarios have been proposed in the literature, for instance, tetraquarks, hybrids, and hadronic molecules which are to be investigated in this work. A hadronic molecular state is a weakly bound system consisting of hadrons. For instance, deuteron is a weakly bound system consist-ing of proton and neutron. In this work, we will study hadronic molecular states made of heavy flavored mesons. Inside such states the constituent mesons stay in a relative S wave and the mass of the state is close to the two meson threshold. Through the study of the strong interactions and radiative decays of these exotic candidates, we expect to learn more information of the internal structure of these states.The hadronic molecular states studied in this work are assumed to consist of heavy-flavored mesons containing heavy-light quarks. In the heavy quark spin symmetry limit the light and heavy quark degrees of freedom are decoupled from each other, and the heavy quark spin and light quark angular momenta are conserved separately. Adapting the effective field theory based on the heavy quark spin symmetry, we will study the intermediate meson loop contributions which are due to the molecular nature of the initial states. This approach will highlight the underlying dynamics and simplify the problem in the numerical calculations.We have studied the intermediate meson loop effects in different decay processes of Zc(3900) and Zc(4020)(we note them as Zc and Z’c later). In the heavy quark spin symmetry limit Zc and Z’c. belong to the same spin doublet and have the same quantum number. The decay of Zc and Z’c share similar features as that of Zb and Z’b. Meanwhile, by comparing the decays of the Zc and Z’c to the same final states, we can extract the internal dynamic information of these two hadronic molecular candidates. Nevertheless, the study of Z’câ†'X(3872)y can serve as an important probe for the internal structure of the Z’c. In particular, the comparison between decays of Z’câ†'X(3872)y and χcJγ would be useful for gaining more information about the Z’c and X(38720) structures.