Decay $\varphi (1020)\to \gamma f_0(980)$: analysis in the non-relativistic quark model approach

Abstract

We demonstrate the possibility of a good description of the processes $\varphi (1020)\to \gamma \pi \pi$ and $\varphi (1020)\to \gamma f_0(980)$ within the framework of non-relativistic quark model assuming $f_0(980)$ to be dominantly quark--antiquark system. Different mechanisms of the radiative decay, that is, the emission of photon by the constituent quark (additive quark model) and charge-exchange current, are considered. We also discuss the status of the threshold theorem applied to the studied reactions, namely, the behaviour of the decay amplitude at $M_{\pi \pi }\to m_{\varphi }$ and $m_{f_0}\to m_{\varphi }$. In conclusion the arguments favouring the $q\bar{q}$ origin of $f_0(980)$ are listed.

Comments: 24 pages, some typos corrected