Electromagnetic decay of glueballs

The magnetic dipole radiative decay of a $J^{\mathrm{PC}}=0^{-+}$ glueball is considered within the MIT bag model. The resultant width, due to gluonic coupling to quarks, is sizable. In addition to $\eta -{\eta }^{\prime }$-glueball mixing, other contributions are found to be significant. We comment that, for magnetic dipole transitions, the radiative widths of glueballs can be expected to be larger than those of radially excited $Q\overline{Q}$ mesons, due to wave-function-orthogonality effects in the latter case.