The Interactions Between The Heavy Hadrons And Mass Spectrum Of The Heavy Hadronic Molecules

The exotic hadronic states have a special position in hadron spectroscopy,studying exotic hadronic states not only gives new insights for revealing the hadron structures,but also provides useful information to deepen our understanding of the nonperturbative behavior of the quantum chromodynamics.Thus,the exploration of exotic hadronic states is the academic frontier of the hadron physics.In the past 20 years,experimentalists have observed more and more charmonium-like states,hidden-charm pentaquark states,and doubly charmed tetraquark state,which have stimulated abundant discussion of exotic hadronic states.Due to the masses of several X/Y/Z/P_c/P_cs/T_cc⁺ states are close to the thresholds of corresponding two hadrons,it is natural to explain them as the heavy hadronic molecules.In this thesis,we first review the research background and related experimental and theoretical research status of the exotic hadronic states,especially the observation of the X/Y/Z/P_c/P_cs/T_cc⁺ states.And then,we introduce the knowledge of the heavy hadronic molecules,one-boson-exchange model,and the effective Lagrangian approach.In the following chapters,we mainly investigate the interactions between the heavy hadrons and mass spectrum of the heavy hadronic molecules,both the S-D mixing effects and coupled channel effects are considered in realistic calculation.Firstly,the observation of charmonium-like states with higher mass and the announced white paper on the future physics program by the BES? Collaboration in 2019 show that experimental searches for charmonium-like states with mass above 4.5 GeV becomes a hot issue.Considering the close relations of XYZ states with hidden-charm molecular tetraquarks,we study S-wave hidden-charm and hidden-strange molecular tetraquarks with the masses around 4.5?4.7 GeV,which are composed of the charmed-strange meson in H-doublet and the anticharmed-strange meson in T-doublet.Additionally,due to the weak decay processes between the ?b?P_c+K and B? XYZ+K are very similar,and the observation of three P_c states can be assigned as the hidden-charm molecular pentaquarks,we convince that the B?XYZ+K could be the appropriate decay process to search the hidden-charm molecular tetraquarks.Although there were abundant charmonium-like structures reported in the B meson weak decays over the years,we have not definitely identify one hidden-charm molecular tetraquark until now.By comparing the experimental data collected from the B?XYZ+K and the mass spectrum and two-body hidden-charm decay channels for the S-wave DD/DsDs-type molecules,we find several possible hints of the existence of the hidden-charm molecular tetraquarks in the B?XYZ+K,and look forward to the future experiments like the LHCb,Belle ?,and BES? collaborations can test our theoretical predictions with more precise experimental data.Secondly,when facing the status of exploring hidden-charm pentaquarks,we naturally expect that there should form a zoo of hidden-charm molecular pentaquarks in the hadron spectroscopy,which is composed of a series of hidden-charm molecular pentaquarks with higher mass and different strangeness.Thus,we systematically investigate various types of hidden-charm molecular pentaquarks from the S-wave B_c^*(?) interactions with B_c^*=?c/?_c^* and (?)=(?)₁/(?)₂^*,?_c^',*(?)_s^* interactions,and ?_c^*,(?)_s^*interactions,and also discuss their two-body strong decay behaviors.By these efforts,we may give theoretical suggestions to search for these new types of hidden-charm molecular pentaquarks in future experiment,and experimental searches for them can be also a crucial test of the hadronic molecular states assignment to the observation of P_c/P_cs states.Furthermore,we focus on the S-wave interactions between a doubly charmed baryon and a charmed meson in T-doublet,and predict possible triple-charm molecular pentaquarks with S-wave?_ccD₁/?_ccD₂^* systems.Thirdly,the LHCb Collaboration reported a new structure T_cc⁺ existing in the D~0D~0?⁺ invariant mass spectrum in 2021,where the T_cc⁺ can be assigned as the isoscalar DD*molecular state with J^P=1⁺,and this observation provides us a good opportunity to construct the family of the doubly charmed molecular tetraquarks.Thus,we systematically study a series of S-wave HT/TT-type doubly charmed molecular tetraquark candidates,and discuss the decay behaviors of these possible doubly charmed molecular tetraquarks,where the obtained crucial information is helpful to the experimental search for the doubly charmed molecular tetraquark states in the future.We hope that the present work can play an important role to construct the family of the heavy hadronic molecules,and encourage experimental studies of searching for heavy hadronic molecules.With the accumulation of more and more experimental data with higher precision,exploring these new types of heavy hadronic molecules will be an interesting and important research issue for both theorists and experimentalists,which will be full of more opportunities and challenges.Additionally,theoretical study of these new types of heavy hadronic molecules is also encouraged by other approaches or different perspectives in the future.These investigations can deepen our understanding of heavy hadronic molecules,and may provide crucial information of searching for heavy hadronic molecules in future experiments with higher precision data.