Study On The Quality Of Hidden Heavy-flavor Tetraquark States

In recent twenty years,more and more heavy hadrons have been discovered experimentally,such as the doubly heavy baryon Ξ_cc and tetraquark state T_cc,as well as other observed XYZ states.After calculating hadron spectra,we can explain internal structures of these hadrons,and predict masses of the other exotic hadrons.Moreover,studying these heavy hadrons can give us deeper understanding of non-perturbative QCD.In this paper,we use a unified MIT bag model to calculate masses of the hidden heavyflavor tetraquark states.The first chapter introduces the standard model of particle physics,the classification and quark model of hadrons.We also introduce heavy-flavor hadrons and multi-quark states discovered in experiments,and the non-perturbative QCD methods.In the second chapter,we show the formalism of the MIT bag model and calculating procedures of hadron masses.A unified calculation method for heavy and light hadron spectra is introduced,which includes short-range chromoelectric interaction（binding energy）and chromomagnetic interaction.We apply this model to the hidden heavyflavor states with two and four heavy quarks.By constructing the color-spin wave function,we derive the formula of hadron masses,the chromomagnetic interaction matrix,and the scaling relation of the binding energy in different color states.In the third chapter,based on the model,we use a set of unified parameters,and add the interaction of color magnetic field and the possible binding energy between heavy quarks.We systematically studied the hidden heavy-flavor tetraquak qQ（?）,QQ’（?）’（q=s,u,d;Q=c,b,Q and Q’ can represent heavy quarks of same flavors）of all the ground state configurations,containing at least two and four heavy quarks.We use the MIT bag model considering chromomagnetic interaction and binding energy,taking into account the mixings due to spin and color.Our calculations show that for J^PC=0⁺⁺,the cccc ground states have 6469 MeV and 6572 MeV,bb（?） ground states have 19685 MeV and 19717 MeV.Among them the mass of ground cc（?）（6572 MeV）is consistent with CMS observed X（6600）=（6552±10±12 MeV）.Then we further calculate ground hidden heavy-flavor tetraquark state system cb（?）、sc（?）、sb（?）、nc（?）、nb（?）,and discuss thier possible decay channels,we also predict that the Z_c（4200）is likely to be hidden heavy-flavor tetraquark state nc（?） with J^PC=1^+-.These results can be tested in the future.The fourth chapter is the summary and prospect of the work of this paper.The advantage of this work lies in the determination of a set of uniform parameters to calculate the mass of the ground state implicit heavy-flavor tetraquark state,and some predictions are given to be verified by experiments.These conclusions and results can be used to improve the model,or to study strange hadronic states with more complex internal structures,related physical images are also instructive.