The radiative decay of scalar glueball from lattice QCD

We perform the first lattice QCD study on the radiative decay of the scalar glueball to the vector mesonφin the quenched approximation.The calculations are carried out on three gauge ensembles with different lattice spacings,which enable us to do the continuum extrapolation.We first revisit the radiative J/ψdecay into the scalar glueball G and obtain the partial decay widthΓ(J/ψ→γG)=0.578(86)keV and the branching fraction Br(J/ψ→γG)=6.2(9)×10^(-3),which are in agreement with the previous lattice results.We then extend the similar calculation to the process G→γφand get the partial decay widthΓ(G→γφ)=0.074(47)keV,which implies that the combined branching fraction of J/ψ→γG→γγφis as small as O(10^(-9))such that this process is hardly detected by the BESⅢexperiment even with the large J/ψsample of O(10^(10)).With the vector meson dominance model,the two-photon decay width of the scalar glueball is estimated to beΓ(G→γγ)=0.53(46)e V,which results in a large stickiness S(G)~O(10^(4))of the scalar glueball by assuming the stickiness of f_(2)(1270)to be one.

Mass spectrum and strong decays of strangeonium in a constituent quark model

In this work we calculate the mass spectrum of strangeonium up to the 3D multiplet within a nonrelativistic linear potential quark model.Furthermore,using the obtained wave functions,we also evaluate the strong decays of the strangeonium states with the ^3P_0 model.Based on our successful explanations of the well established states φ(1020) , φ(1680) , h_1(1415) , f'_2(1525) ,and φ_3(1850) ,we further discuss the possible assignments of strangeonium-like states from experiments by combining our theoretical results with observations.It is found that some resonances,such as f_2(2010) and f_2(2150) ,listed by the Particle Data Group,and X(2062) and X(2500) ,newly observed by BESIII,may be interpreted as strangeonium states.The possibility of φ(2170) as a candidate for φ(3S) or φ(2D) cannot be excluded.We expect our results to provide useful references for looking for the missing s\bar{s} states in future experiments.

Glueball spectrum from Nf=2 lattice QCD study on anisotropic lattices

The lowest-lying glueballs are investigated in lattice QCD using Nf = 2 clover Wilson fermions on anisotropic lattices. We simulate at two different and relatively heavy quark masses, corresponding to physical pion masses of mπ～938 MeV and 650 MeV. The quark mass dependence of the glueball masses has not been investigated in the present study. Only the gluonic operators built from Wilson loops are utilized in calculating the corresponding correlation functions. In the tensor channel, we obtain the ground state mass to be 2.363（39） GeV and 2.384（67）GeV at mπ～938 MeV and 650 MeV, respectively. In the pseudoscalar channel, when using the gluonic operator whose continuum limit has the form of ∈_ijkTrB_iD_jB_k, we obtain the ground state mass to be 2.573（55） GeV and 2.585（65） GeV at the two pion masses. These results are compatible with the corresponding results in the quenched approximation. In contrast, if we use the topological charge density as field operators for the pseudoscalar, the masses of the lowest state are much lighter（around 1 GeV） and compatible with the expected masses of the flavor singlet qq meson. This indicates that the operator ∈ijk TrBiDjBk and the topological charge density couple rather differently to the glueball states and qq mesons. The observation of the light flavor singlet pseudoscalar meson can be viewed as the manifestation of effects of dynamical quarks. In the scalar channel, the ground state masses extracted from the correlation functions of gluonic operators are determined to be around 1.4-1.5 GeV, which is close to the ground state masses from the correlation functions of the quark bilinear operators. In all cases, the mixing between glueballs and conventional mesons remains to be further clarified in the future.