Study of the pseudoscalar glueball in J /ψ radiative decays

Abstract

We aim to explore the production rate of the pseudoscalar glueball in J/ψ radiative decay by lattice quantum chromodynamics in quenched approximation. The calculation is performed on three anisotropic lattices with the spatial lattice spacing ranging from 0.222(2) fm to 0.110(1) fm. As a calibration of some systematical uncertainties, we first extract the M1 form factor V^(0) of the process J/ψ→γηc and get the result V^(0)=1.933(41) in the continuum limit, which gives the partial width Γ(J/ψ→γηc)=2.47(11) keV. These results are in agreement with that of previous lattice studies. As for the pseudoscalar glueball G0-+, its mass is derived to be 2.395(14) GeV, and the form factor V(0)^ of the process J/ψ→γG0-+ is determined to be V^(0)=0.0246(43) after continuum extrapolation. Finally, the production rate of the pseudoscalar glueball is predicted to be 2.31(90)×10-4, which is much smaller than that of conventional light qq̄ η states. After the subtraction of the phase space factor, the couplings of J/ψXγ are similar where X stands for η states and the pseudoscalar glueball. Possibly, the UA(1) anomaly plays an important role for the large couplings of gluons to the flavor singlet η states in J/ψ radiative decays.