Coupled-channel Calculation On Mass Spectra And Strong Decays Of Double Heavy Flavor Mesons

Hadron spectroscopy and decay,reflecting the structural information inside the hadron,are not only an important tool to understand the internal structure and dynamics of the hadron but also a significant topic of hadron physics.Quantum chromodynamics?QCD?has been widely recognized as the basic theory of strong interactions.However,in the low-energy region,the QCD is highly non-perturbative.Thus,there exist some difficulties to obtain the low-energy structural properties of hadrons by strictly solving QCD.The QCD-inspired quark model is still a powerful tool to deal with low-energy strong interaction systems,and at least take rather success in the prediction of low-energy heavy flavor hadron spectra below the open charm threshold.In the recent decade,a large number of heavy flavor meson resonances have been discovered by international collaborations in international scientific apparatus.Among them,about twenty heavy hadron states,the so-called XYZ states,are not completely consistent with the expectations of the traditional component quark model theory.Above the first open flavor threshold,the prediction of constituent quark model is not consistent with experiment value.Many heavy hadrons of the theoretically predicted has not been discovered and a lot of the heavy hadron are difficulty to specify in the constituent quark model.The constituent quark model faced difficulties to interpret these so-called exotic heavy flavor hadron states,which prompt our to consider whether the quark interaction potential truly reflects the low-energy region quark dynamics.Indeed since the earliest days of hadron spectroscopy,it has been recognized that properties of hadron can be strongly influenced by meson-meson continuum state.The so-called non-quenched quark model containing high Fock state components can conveniently determine whether hadron resonance is a multi-quark state,or a mixture of ordinary hadron and multi-quark state.It is expected that it can calculate the mass spectra of the heavy flavor mesons in the unified model framework,thus identifying the structure of the heavy flavor hadron.However,the study of the heavy flavor meson spectra and its strong decay involves complex coupling channel calculations that deserve further research.We study the charmonium state and charmonium-like state mass spectrum and strong decay width in coupled-channel model.We use the model to calculate the influence of the coupled-channel effect on the charmoium,which found the composition of the meson continuum states has a great affected in the charmoium spectrum.Through comparing two quark model predictions with the experimental observations we found that two model have similar result below the threshold of charmoium.Therefore,we speculate the large mass shift can be absorbed into the redefinition parameters.However,the coupled-channel model can give good result for these charmonium-like state around the thresholds.In our coupled-channel model,forJ^PC=1^--family we not only considered coupling of S-D wave caused by tensor term but also taken the couple-channel effect into account result from mixing between the cc states and continuum states.According to the mass spectra of charmonium states predicted by the couple-channel model,the X?3872?is interpreted as a mixture of 78.98%meson-meson continuum states and 21.02%P state charmonium.The X?4160?is interpreted as a mixture of 7.35%meson-meson continuum states and 92.65%D state charmonium.For the state Y?4660?,although predicted the mass in couple-channel model is compatible with the experimental value,the calculated strong decay width is smaller than experiment data.So the strong decay width of Y?4660?need more studies.In couple-channel model,the X?3930?may be assigned as the mixing of 75.37%P state charmonium,0.04%F state chatmonium and 24.27%two-meson continuum components.