experimental results of [@Barberis:1998by].[]{data-label="Fig:10"}](fig10.eps "fig:"){width="50.00000%"}\

Conclusions
===========

We have carried out a study of the production of the $f_1(1285)$ and decay into $\pi a_0(980)$ and $K^*\bar K$ modes. We have studied the cross sections as functions of the $f_1(1285)$ mass, $M_{\rm inv}$, up to 1500 MeV and we have observed two relevant features:

-   The $K^*\bar K$ mode (allowing the $K^* \to K\pi$ decay) has two peaks as a function of $M_{\rm inv}$, one at the $f_1(1285)$ mass and the other one at about 1420 MeV, this latter one with a width of about 60 MeV.

-   The $\pi a_0(980)$ mode has a peak at 1285 MeV and a broad shoulder around 1400 MeV, which comes from a triangle singularity involving $K^* K \bar K$ as intermediate states, and tied to the nature of the $f_1(1285)$ as a $K^* \bar K$ molecule, a sufficient although not necessary condition, since what matters is that the $f_1(1285)$ couples to $K^* \bar K$ and this is known experimentally from the $K \pi \bar K $ decay mode. The combination of the tail of the $f_1(1285)$ with the increased phase space for the $K^* \bar K$ production is the reason for this second peak.

