We formulate an extended linear $sigma$ model of a quarkonia nonet and a tetraquark nonet as well as a complex iso-singlet (glueball) field to study the low-lying scalar meson. Chiral symmetry and $U_A(1)$ symmetry and their breaking play important r
ole to shape the scalar meson spectrum in our work. Based on our study we will comment on what may be the mass of the lowest possible scalar and pseudoscalar glueball states. We will also discuss on what may be the nature of the sigma or $f_0(600)$ meson.
The possibility of the $0^+$ $etaeta$ resonance $f_0(2100)$ as a candidate of the $Q^2bar{Q}^2$ state $C^{ss}(36)$ is explored. The $etaeta$ channel of $f_0(2100)$ is the dominant decay mode, $etaeta$ channel has less decay rate, the decay rate of th
e $etaeta$ channel is very small. The $pipi,;Kbar{K},;4pi$ modes are at next leading order in $N_C$ expansion. Other possible decay modes are discussed.
A chiral field theory of $0^{-+}$ glueball is presented. By adding a $0^{-+}$ glueball field to a successful Lagrangian of chiral field theory of pseudoscalar, vector, and axial-vector mesons, the Lagrangian of this theory is constructed. The couplin
gs between the pseodoscalar glueball field and mesons are via U(1) anomaly revealed. Qualitative study of the physical processes of the $0^{-+}$ glueball of $m=1.405textrm{GeV}$ is presented. The theoretical predictions can be used to identify the $0^{-+}$ glueball.
A chiral field theory of $0^{-+}$ glueball is presented. The coupling between the quark operator and the $0^{-+}$ glueball field is revealed from the U(1) anomaly. The Lagrangian of this theory is constructed by adding a $0^{-+}$ glueball field to a
successful Lagrangian of chiral field theory of pseudoscalar, vector, and axial-vector mesons. Quantitative study of the physical processes of the $0^{-+}$ glueball of $m=1.405textrm{GeV}$ is presented. The theoretical predictions can be used to identify the $0^{-+}$ glueball.
We calculate the mass of $0^{-+}$ triple-valence-gluon resonance, the trigluon glueball, with QCD sum rules. Its mass is found to be approximately in the region between 1.9 GeV and 2.7 GeV with some theoretical uncertainties. Moreover, it is likely t
hat the new BES measurement of the $p bar{p}$ enhancement near threshold in the $J/psi$ decays exhibits the behavior of this trigluon state. Our analyzes favor the baryonium-gluonium mixing picture for the BES observation.