Double Heavy Flavor Tetraquark In The Constituent Quark Model

Hadron spectrum is an important tool to recognize the internal structure and dynamics of hadrons.At present,quantum chromodynamics(QCD)is the most basic theory for studying hadronic properties.QCD has three basic features:asymptotic freedom,color confinement and spontaneous breaking of chiral symmetry.High energy process can be treated by employing perturbation QCD due to asymptotic freedom.However,the theoretical study on hadron spectrum need to develop non-perturbative method due to the nonperturbative effect of QCD at the low energy region.In present,various QCD effective theory or mode have been suggested and include lattice gauge theory,QCD sum rules and constituent quark model.,among which the QCD-inspired constituent quark model has taken excellent success in the low excited states of convent hadron states,namely meson which consist of quark and antiquark and baryon of three quarks.However,in the decade,large numbers of heavy flavor hadron resonances observed newly in the updated scientific facilities.Many states of them is very difficult to be explain in the convent quark model.Above the first open flavor threshold,the prediction of constituent quark model is not consistent with experiment value.Many heavy hadron of the theoretically predicted has not been discovered and a lot of the heavy hadrons are difficulty to specify in the constituent quark model.For this,molecular states,a mixture of molecule and charmonium,and tetraquark have been widely studied for identifying these so called charmoium-like states.In this thesis,the constituent quark model is extended to study the double charm tetraquark.Usually,the tetraquark is treated as two-body interaction between diquark in color anti-triplet and antidiquark in color triplet.Here,the tetraquark is considered as the four-body system with the mixing of various color configurations.The variant method is adopted to solve the four-body Schrodinger equation to obtain the mass spectra.Based on the theoretical calculations,we identify which charmonium-like states may be the tetraquark.The results show that X(3872),X(4140)and so on may be double charm tetraquarkThis thesis is consists of four parts:the first part is an introduction,which briefly describes the history of particle physics,the commonly used NQCD method and charmoium-like states.The second part introduces the potential,the one gluon exchange potential and the linear confinement potential.A completely relativistic corrections of orderv~2/c~2is constructed from the idea of mixing scalar and vector.The relativistic quark model is more accurate in describing the quark system with light quarks.The third part introduces the numerical calculation method,the application of harmonic oscillator basis expansion method in the two-body and four-body schrodinger equations.The parameters are obtained by fitting the ground state of the heavy flavor meson.The parameters are put into the four-body system and the mass spectrum of the double charm tetraquark is obtained by using variational method.The fourth part is to analyze the mass spectrum of the double charm tetraquark with different structures.