On Radiative $\varphi \to \eta \gamma$, $\varphi \to {\eta }^{\prime }\gamma$ Decays

Abstract

We use QCD sum-rules to study the decays $\varphi \to \eta \gamma$ and $\varphi \to {\eta }^{\prime }\gamma$, obtaining $\mathcal{B}(\varphi \to \eta \gamma )=(1.15\pm 0.2)10^{-2}$ and $\mathcal{B}(\varphi \to {\eta }^{\prime }\gamma )=(1.18\pm 0.4)10^{-4}$, in very good agreement with existing experimental data. We also discuss the issue of $\eta -{\eta }^{\prime }$ mixing, predicting the $\eta$ and ${\eta }^{\prime }$ decay constants in a mixing scheme in the quark-flavour basis.

LatTeX, 6 pages. Talk given by F. De Fazio at LNF Spring School in Nuclear, Subnuclear and Astroparticle Physics, 15-20 May 2000 Frascati - Italy Some typos corrected