Investigations On The Spectrum And Decays Of Several Low-lying Double-charm Pentaquark States

The hadron family has two major branches,mesons and baryons.The internal structure of hadrons contains complex quark-gluon structures.In the seventies,Quantum Chromodynamics?QCD?,which describes the theory of strong interaction dynamics between quarks and gluons,was born.According to QCD theory,quarks,antiquarks and gluons in hadrons are continuously transformed and reach a certain balance through interaction.Scientists applied perturbation QCD for the first time in studying the decay process of bound J/?mesons containing charmed quarks.Therefore,QCD is proved to be a successful theory to describe the phenomenon of strong interaction.However,the perturbation QCD algorithm can only be applied to energy and momentum above one or several GeV.In order to fully understand the non-perturbation region of low-energy hadron physics,lattice gauge theories and QCD sum rules have been proposed one after another.However,when describing?mesons,since?mesons do not have mass under the chiral symmetry of spontaneous breaking,the Compton wavelength is greater than 10^-13cm,so infinite lattice must be satisfied.The lattice QCD requires that the spacing between lattice points is much smaller than the size of hadrons(10^-13cm),so the number of lattice points satisfied by?mesons requires higher computer performance and more complex computer programs.People also try to find phenomenological models based on QCD theory to solve the physical dilemma.The most noticeable model is the constituent quark model,which includes two types according to its dynamics:relativistic constituent quark model and non-relativistic constituent quark model.The constituent quark model has successfully explained various physical phenomena for many times.For example,without considering the confinement potential of the harmonic oscillator,the constituent quark model can well describe the spectrum of nucleon,baryon resonances?and strange hyperons by exchanging the Goldstone bosons related to the hidden approximate chiral symmetry of QCD.Now,we use the constituent quark model to investigate the spectrum of several low-lying double-charm pentaquark states.The SU?6?constituent quark model can successfully explain the spectrum,spin and electromagnetic phenomena of hadrons.However,the mass order inverse of the hadron resonances N^*?1440?,??1405?and N^*?1535?cannot be explained.Moreover,some resonances of hadrons predicted by this model have not been found in experiments for a long time,thus causing the problem of"missing states".Up to now,researchers are still not sure whether the theory is insufficient or the experimental accuracy is not high,but we can deepen our understanding of baryon resonances from two angles.On the other hand,QCD theory does not treat multi-quark states?e.g.,pentaquark configurations?differently.During the dispute over the existence of?particles,scientists have gradually devoted themselves to studying the pentaquark configurations of hadrons and hadron excited states.With the increasing accuracy of physical experiments,people have considered the contributions of the higher Fock states on the basis of the three-quark model.In recent years,researchers have predicted that the ccsq??? pentaquark state may form sizable components of the observed five ?_c⁰ resonances by the LHCb Collaboration.In the form of hyperfine interactions in the GBE,we have predicted the spectrum and configuration mixing coefficients of the low-lying ccsq??? configurations with J^P=1/2^-?J^P=3/2^- and J^P=5/2^- using similar theoretical methods.The numerical results show that the effect of configuration mixing with the same spin angular momentum and parity on the energy of the mixed state cannot be ignored.We modified the oscillator frequency,and even changed the coupling strength parameter of meson exchange from 0%to 10%to avoid the dependence of the results on the model parameters.The predicted value is very close to the mass spectrum of the double-charm pentaquark state predicted by other researchers.However,the main configuration occupation in the configuration mixing coefficient is almost the same.In addition,the decay channels coupling amplitudes of pseudoscalar mesons and baryons are described by these pentaquark configurations using the chiral Lagrange approach.