Radiative $\varphi$$-$meson decays and $\eta$-${\eta }^{\prime }$ mixing: a QCD sum rule analysis

Abstract

The radiative transitions $\varphi \to \eta \gamma$ and $\varphi \to {\eta }^{\prime }\gamma$ are analysed using QCD sum-rules. The results we obtain for $\mathcal{B}(\varphi \to \eta \gamma )=(1.15\pm 0.2)10^{-2}$ and $\mathcal{B}(\varphi \to {\eta }^{\prime }\gamma )=(1.18\pm 0.4)10^{-4}$ are in very good agreement with existing experimental data. The related issue of $\eta -{\eta }^{\prime }$ mixing is discussed and we give predictions for the $\eta$ and ${\eta }^{\prime }$ decay constants in the framework of a mixing scheme in the quark-flavour basis.

Comments: Latex, 15 pages, 3figures. Some typos corrected