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The Ds+→a0(980)e+ve,(?)s~0→J/ψa0(980) Decays And The A0(980)-f0(980) Mixing

Posted on:2022-12-03Degree:MasterType:Thesis
Country:ChinaCandidate:J X LinFull Text:PDF
GTID:2480306770975779Subject:Chemistry
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It is an important subject in the field of hadron physics to study the internal structure,properties of hadrons and the mechanism of strong interaction between hadrons.The simplest structures of hadrons are the conventional qq meson state composed of a quark and an antiquark and the conventional qqq baryon state composed of three quarks.Most of the hadron states found experimentally can be explained as conventional hadron states.With the improvement of experimental detection technologies and accelerators energy,many hadrons that cannot be explained well by conventional hadron states have been found in experiments,and they may be exotic hadrons with more complex structures.Studies on exotic hadrons can provide more information about the strong interaction between gluon and quark and the internal structure of hadrons.The light scalar mesons f0(500),f0(980)and a0(980)are considered as candidates of exotic hadron states,with spin-parity JPC=0++ and strangeness S=0.In the framework of the chiral unitary approach(CHUA),the f0(500),f0(980)and a0(980)states can be dynamically generated from the pseudoscalar-pseudoscalar s-wave interaction.They are interpreted as meson-meson molecular states,with ππ the main component of f0(500),KK the main component of f0(980),and a0(980)coupling mostly to channels KK and πη.In this thesis,basing on the molecular picture of the f0(980)and a0(980)states,the production rates of a0(980)in the semileptonic Ds+→e+ve a0(980)(f0(980))decays and nonleptolic Bs0→J/ψπ0η(π+π-)decays are studied,in the framework of the CHVA,with the aim of testing the molecular picture of the a0(980)and f0(980)states.Starting from the reaction mechanism on the quark level for the semileptonic Ds+ decay and the nonleptonic Bs0 decay,the KK and ηη states are produced after the hadronization by introducing a qq pair with the quantum numbers of the vacuum.And then the a0(980)and f0(980)states are generated dynamically from the rescattering of KK,ηη and the coupled channels.The ratios of Γ[Ds+→e+ vea0(980)0,a0(980)0→π0η]/Γ[Ds+→e+vef0(980),f0(980)→π+π-]and Γ[Bs0→J/ψa0(980)0,a0(980)0→π0η]/Γ[Bs0→J/ψf0(980),f0(980)→π+π-]are evaluated to cancel the unknown factor involving the vertices of weak interaction.Using the experimental branching ratios for D+s→e+vef0(980),f0(980)→π+π-decay and Bs0→J/ψf0(980),f0(980)→π+π-decay from the Partical Data Group(PDG),the branching ratios for the Ds+→e+vea0(980)0,a0(980)0→π0η decay and the Bs0→J/ψa0(980)0,a0(980)0→π0η decay are predicted theoretically.The branching ratio Br[Ds+→e+vea0(980)0,a0(980)0→π0η]obtained theoretically is in good agreement with the experimental measurement of BESⅢ,supporting the molecular pictures of the a0(980)and f0(980)states.We also study the isospin violation or a0(980)-f0(980)mixing in the semileptonic Ds+→e+ vea0(980)(f0(980))decays and the nonleptonic Bs0→J/ψa0(980)(f0(980))decays.The Ds+→e+vea0(980)and Bs0→J/ψa0(980)decays with isospin violation can be happened from the isospin conserved Ds+→e+vef0(980)and Bs0→J/ψf0(980)decays through the a0(980)-f0(980)mixing.It is shown that the isospin violation is about 3%~4%both in the semileptonic Ds+ decay and the nonleptonic Bs0 decay investigated here.Two sources of isospin violation are found in this thesis:one is the mass difference between the charged koan and the neutral koan in the explicit KK loops,and the other one is the mass difference between the koans in transition T matrix.The numerical results show that the isospin violation effect caused by the latter is more significant than that of the former.This means that the Ds+→e+vea0(980)0,a0(980)0→π0η decay and Bs0→J/ψa0(980)0,a0(980)0→π0ηdecay with isospin violation are very sensitive to the generation mechanism of the light scalar mesons and their nature.Therefore,these two decay processes are ideal places to test the internal structure of light scalar mesons and the low-energy effective theory of strong interactions.The results obtained in this thesis provide a theoretical reference for the future precise measurements of these two decay processes,which are important and necessary.The accurate information about the decay branching ratio,the shape of the invariant π0η mass distribution and the a0(980)-f0(980)mixing are helpful to further test the nature of the f0(980)and a0(980)states and to further understand the non-perturbativ properties of the strong interaction in the low-energy region.
Keywords/Search Tags:strong interaction, light scalar mesons, chiral unitary approach, molecular state, isospin violation
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