On the gluon content of the eta and eta' mesons

Abstract

A phenomenological analysis of radiative $V\to P\gamma$ and $P\to V\gamma$ decays is performed with the purpose of determining the gluonic content of the $\eta$ and ${\eta }^{\prime }$ wave functions. Our results show that within our model there is no evidence for a gluonium contribution in the $\eta$, $Z_{\eta }^2=0.00\pm 0.12$, or the ${\eta }^{\prime }$, $Z_{{\eta }^{\prime }}^2=0.04\pm 0.09$. In terms of a mixing angle description this corresponds to ${\varphi }_P=(41.4\pm 1.3{)}^{\circ }$ and $|{\varphi }_{{\eta }^{\prime }G}|=(12\pm 13{)}^{\circ }$. In addition, the $\eta$-${\eta }^{\prime }$ mixing angle is found to be ${\varphi }_P=(41.5\pm 1.2{)}^{\circ }$ if we don't allow for a gluonium component.

Comments: 16 pages, 3 figures, JHEP style. First part of data fitting changed, conclusions not modified