[en] Based on 58M BESII J/ψ data, J/ψ → ωπ⁺π^- and J/ψ → K-bar^*(892)K⁺π^- channels are studied. Clear low mass enhancements in the invariant mass spectra are observed in both channels. These low mass enhancements do not come from backgrounds of other J/ψ decay channels, nor from phase space effect. PWA analyses show that the low mass enhancement in J/ψ → ωπ⁺π^- is a 0⁺⁺ resonance with mass 487 ± 68 MeV and width 363 ± 131 MeV which is believed to be the σ particle, and the low mass enhancement in J/ψ → K^*(892)Kπ is a 0⁺ resonance with mass 877 ± 85 MeV and width 346 ± 89 MeV which is believed to be the κ particle. (author)

[en] We summarize some features of the vector meson dominance model which was recently proposed for studying radiative decays involving the scalar mesons. Using the experimental values of Γ(a₀ → γγ), Γ(f₀ → γγ) and Γ(φ → a₀γ) as inputs, we show that the model predicts a large hierarchy between Γ(a₀ → ωγ) and Γ(a₀ → ργ) as well as between Γ(f₀ → ωγ) and Γ(f₀ → ργ). (author)

[en] The quark-level linear σ model (LσM) is employed to compute a variety of electromagnetic and weak observables of light mesons, including pion and kaon form factors and charge radii, charged-pion polarizabilities, semileptonic weak K_l3 decay, semileptonic weak radiative pion and kaon form factors, radiative decays of vector mesons, and nonleptonic weak K_2π decay. The agreement of all these predicted observables with experiment is striking. In passing, the tight link between the LσM and vector-meson dominance is shown. (author)

[en] The Kπ and K^*π mass spectra and the (K, π) angular distributions obtained by 58M J/ψ-data in BESII(V103) for the relevant J/π decay process are analyzed by using a simple field theoretical model (the VMW method). A strong evidence for production of the low mass iso-spinor scalar meson, κ(800 - 900) with mass approx. = 850 MeV and width approx. = 300 MeV, has been obtained. (author)

[en] The glueballs, which are bound states of gluons, are predicted by QCD. However, up to now, we do not know which mesons are pure glueballs, though there are many candidates of glueballs and mixed states of glueballs. Based on BESI and BESII data, many meaningful research on glueballs was performed and some interested results are obtained, especially on f₀(1500), f₀(1710) and ξ(2230). This talk review some recent progress on glueball search at BES. (author)

[en] The J^pc = 1^-+ mesons are cleary SU(3) non-qq-bar exotic mesons because they can be never former by a pair of quark and anti-quarks. At least two 1^-+ mesons have been already reported around 1.5 GeV. The experimental results of the 1^-+ exotic mesons are briefly reviewed and their new interpretation is proposed. (author)

[en] The spectroscopy of light-quark vector mesons with the lower mass region (≤ 1.8GeV) seems to be still in confusion. We review spectrum of this sector in the covariant classification scheme, where the two vector-nonets V^(N) and V^(E) exist in the ground states, and point out that the extra-vectors, ρ^(E) and ω^(E), have the decay properties consistent to be identified, respectively, with ρ(1250) and ω(1250), the controversial mesons. (author)

[en] We discuss the properties of the nucleon (N) and its excited state with odd parity (N*) under the aspect of chiral symmetry, identifying them with suitable representations of the chiral group. It is shown that there are two distinctive schemes to assign the chiral multiplet to N and N*. We construct linear σ models for N and N* with the two assignments to show their physical implications. We also discuss the in-medium properties of N(1535), comparing the present mode with the other chiral model based on the different picture of N*. (author)

[en] Our method of analysis, which led to existence of σ and κ mesons, is reviewed and examined from a viewpoint of general S-matrix. It is shown that the method is consistent with the constraints from chiral symmetry and unitarity. Accordingly the long-believed common analyses of ππ(Kπ) scattering and production processes, based on elastic unitarity, prove to lose its theoretical base. The observed phase motion by 180 degrees of σ shows also the validity of our method. (author)

[en] In a covariant level-classification scheme of hadrons proposed recently, the existence of ''chiral particles'', scalar and axial-vector mesons as the partners of the ground-state pseudo-scalar and vector mesons, respectively, were predicted in D and B meson systems, realizing a linear representation of chiral symmetry concerning the light quarks. In this work we reanalyze the D*π mass spectra obtained through Υ(4S) and Z⁰ decay and the Bπ spectra obtained through Z⁰ decay to show the possibility of the existence of D₁^χ and B₀^χ, respectively. This talk is a review of essential points of our previous work. (author)