Theoretical Study On The Properties Of X(4140), X(4160)and ?(2170)

Particle physics is the frontier of physics,which mainly study the elementary particles and their interactions.As an important part of particle physics,hadron physics focuses on the exploration of strong interactions.In last decades,many resonances that cannot be explained by the quark model have been found experimentally.How to interpret the resonances found in experiments is crucial to understand the interactions between hadrons.In the Quantum Chromodynamics,some exotic states beyond the quark model are allowed,such as multi-quark states,hybrid states,molecular states,gluon-ball,etc.Further study of these exotic states will greatly help us to study the strong interaction.Many chromium-like states are the possible candidates of exotic states,which exhibit some properties that are markedly different from those of traditional mesons.In this thesis,we will focus on the nature of the charmonium-like states X(4140)and X(4160)in the process Ab?J/???.For the measurements of process B+?J/??K+ K+by the LHCb Collaboration,we can see the X(4140)resonance with a large width in the J/?? mass distribution.This is quite different from the data of CMS,CDF and D0 Collaboration.In the previous study of our research group,we have provided a reasonable explanation of the LHCb measurements by considering the contributions from the X(4160)and the X(4140)with a narrow width.This leads us to expect that a similar structure can be observed in the J/?? invariant mass distribution of the weak decay process of ?b.The measurements of this process by the CMS Collaboration also made it possible to conduct further research.In this work,we use the unitary coupled-channel approach,and take the X(4160)state as a Ds*Ds*molecular state which is dynamically generated from the hadronhadron interaction.We studied the decay of ?b?J/??? by considering the intermediate resonances X(4140),X(4160)and Pcs(4459),and calculated the J/?? mass distribution.In addition to the peak of the X(4140),we also found a bump structure around 4160 MeV followed by a cusp structure around Ds*Ds*threshold in the J/?? invariant mass distribution,which can be associated to the Ds*Ds*molecular state X(4160).We also calculated the ?b? Ds*Ds*? mass distribution,and found an enhancement structure near the Ds*Ds*threshold which is a feature of the Ds*Ds*molecular state X(4160).On the other hand,the study of light vector mesons in higher energy region has always been a hot topic in both experiment and theory.For example,there are many theoretical explanations of the ?(2170),including the highly excited state of ?,tetraquark and molecular state.Available experimental data cannot distinguish these interpretations,and the radiative decay data of mesons are helpful to distinguish these theories.So we studied the radiative decays of some light vector mesons with the vector meson dominance.The decay branch ratio of some light vector mesons has been calculated with the experimental data,the results are helpful for us to measure the decay of light vector mesons and understand their nature,and further research requires more experimental measurements.In summary,this work is of great importance for our understanding of the properties of the charmonium-like states X(4140)and X(4160),we support that X(4160)as a molecular state generated by the dynamics of meson-meson interaction will play an important role in the invariant mass spectrum of J/??.This work also provides a theoretical basis for further experimental study on the radiation decay of light vector mesons.