Study On Production And Spectrascopy Of Heavy Exotic Hadron States

The traditional quark model divides hadrons into baryons consisting of three quarks and mesons consisting of a quark and an antiquark.Hadrons that can not be interpret-ed by the traditional quark model are commonly referred to as exotic hadrons.These exotic hadrons are not excluded by quantum chromodynamics,they include multi-quark hadrons and hadrons obviously affected by the coupling channel effect.Potential mod-el have given good explanations and predictions for the properties of ordinary baryons and mesons,but after 2003,more than 30 heavy-flavoured exotic hadrons exceeding the quark model,such as X(3872),Y(4260)and Z,(3900)have been found experimentally.The LHCb group has published two hidden charm hadron states Pc(4380)and Pc(4450),recently the existence of three five quark hadrons states Pc(4312),Pc(4440)and Pc(4457)have been confirmed by higher statistical data.In order to underst,and the st.ructures of these exotic hadron states,many explanations have been put forward:1)the-compact tetraquark.diquark-antidiquark and molecular scheme for XY Z hadrons;2)the compact pent,aquark,multiple quark groups,meson-baryon molecular state for exotic baryons such as hidden charm Pc;3)the glueball and hybrid state formed by gluon self-interaction are also possible explanations for the structures of exotic hadrons;4)the existence of the coupling channel effect will lead to the superposition of several fock states with the same quantum numbers and similar masses,which will lead to the appearance of the anomalous masses of hadron states,which is another explanation for the exotic hadron states.The discovery of exotic hadron states broadens our vision of hadrons and provides an impor-tant window to deepen our understanding of strong interactions.Therefore,systematic study of the mass spectrum,production and decay of exotic hadrons is of great signif-icance to understand the reason of quark confinement and the fundamental problem of how quarks and gluons form hadrons and is also important way for people to understand the nature of strong interactions.The main purpose of this dissertation is to study the mass spectra and properties of exotic hadron states(especially compact pentaquark and tetraquark states)and their production mechanism.The quark composition of the hidden charm five quark hadron Pc observed experi-mentally is ccuud,it produces in decay of Ab,the direct production at parton level is probably another production mechanism,this dissertation studies the production pro-cesses of Pc(4380)in different energy regions in the electron-positron collider.The search for new hadron states is of great significance for understanding the hadron structures,if the interchange of light and heavy quarks of the Pc state is carried out,the Pc ’s mirror states QQQqq(Q=b,c,q=u,d,s)can be obtained,in this dissertation,the possibilities of existence,mass spectra and stabilities of these systems are studied in detail under the framework of the chromomagnetic interaction(CMI)model.In addition,X(5568)is a exotic meson with four quarks of different flavors observed by the DO group,which needs to be confirmed by other experimental groups,this dissertation systematically studies this new possible structure under the same theoretical framework.The research results of this dissertation include two parts,now they are summarized as follows:1.Pc(4380)production in the electron-positron collider This dissertation studies the following two production processes of Pc(4380):The results show that when the energy of the center of mass system is 10.6 GeV(KEK B factory)and 91.2 GeV(Z boson resonance energy region),there may be an obvious production signal of Pc(4380).At the energy of 10.6 GeV,process(1)has a larger scatter-ing cross section(152.7 fb),and the contribution of process(2)can be neglected;at the energy of 91.2 GeV the cross section value of process(2)is about 300 fb,and process(1)contributes only about 10 fb.In addition,we systematically study the dependence of the production cross section on hadronization matrix elements,the scattering angle of final Pc state,the spin of charm quark pairs,the types of accompanying quark pairs and the scattering sub-amplitude.Our results show that it is feasible to find the hidden charm pentaquark states Pc in the electron-positron collider.2.Mass spectra of exotic hadron states and their propertiesIn this dissertation,the chromomagnetic energy of the pentaquark states QQQqq con-taining three heavy quarks is systematically studied,the mass spectra of the systems are obtained,and the stabilities of all eigenstates of mass are analyzed.It is found that these eigenstates are difficult to form compact narrow-width pentaquark states due to insuffi-cient attraction between quarks and can occur rearrangement decay,this indicates that the QQQqq systems tend to have shallowly bound molecular state structures.Based on the mass spectra of the QQQqq systems,the upper mass limits of all ground triple heavy baryons ΩQQQ are still obtained.In this dissertation,the mass spectra of tetraquark systems with four different quark flavors q1q2q3q4 are systematically studied.It is found that the strong interaction between light quarks within the systems brings about larger splittings of chromomagnetic energy,resulting in the masses of lower eigenst ates in the spectra being lower than the sum of the corresponding threshold mesons’ masses,which indicates that these systems can form narrow-width compact tetraquarks and these s-tates have the value of being sought experimentally.We find that the masses of busd systems are higher than that of X(5568)published in the experiment,this result does not support the existence of X(5568).In additio,the effective attraction and repulsion inside the multi-quark states,the dependence of effective quark masses on hadron environ-ments and the branch ratios of rearrangement decays are analyzed and discussed in detail.