| Basis Light-Front Quantization(BLFQ)has already been used with success to study various mesons and baryons.Compared with QCD and other theories,the main strength of BLFQ is: that one can be used to study hadronic structures in many Fock sectors,and each space can contain many particles.In this paper,we apply the BLFQ to study the newly discovered tetraquark state,X(6900),which consists of two charm and two anti-charm quarks.The discovery of X(6900)makes this all-charm tetraquark state one of the most unique tetraquark states.In this work,in order to explore the internal structure of X(6900)more comprehensively and accurately,we consider not only the exchange antisymmetry of identical particles,but also the color dependence of confinement potential.Using the BLFQ method,we obtain the Hamiltonian matrix with different truncation parameters,and diagonalize them to obtain the lowest mass of the tetraquark and the values of the charmonium.In the case of a single charmonium,we get the threshold when all the interactions between mesons are included and the threshold of c(?) when the interactions between c and (?) are turned off.In the case of the tetraquark state,we obtain the tetraquark state mass with all interactions between particles,the tetraquark state mass without any interactions between particles,and the tetraquark state mass with only c(?) particle pair 13 and particle pair 24 interactions.We fit the masses in different cases.The tetraquark masses that we obtain and including the points extrapolated by fitting,are much higher than the estimates of all thresholds.This shows that the ground state four quarks in our model are not deeply bound,but can be decomposed into two charmonium states. |
