The ${\Omega }_c\to {\pi }^{+}({\pi }^0,\eta )\pi {\Xi }^{\ast }$ reactions and the two $\Xi (1820)$ states

Abstract

We have studied the ${\Omega }_c\to {\pi }^{+}({\pi }^0,\eta )\pi {\Xi }^{\ast }$ decays, where the final $\pi {\Xi }^{\ast }$ comes from the decay of two resonances around the nominal $\Xi (1820)$, which are generated from the interaction of coupled channels made of a pseudoscalar and a baryon of the decuplet. The $\pi {\Xi }^{\ast }$ mass distributions obtained in the six different reactions studied are quite different and we single out four of them, which are free of a tree level contribution, showing more clearly the effect of the resonances. The lower mass resonance is clearly seen as a sharp peak, but the higher mass resonance manifests itself through an interference with the lower one that leads to a dip in the mass distribution around $1850\mathrm{MeV}$. Such a feature is similar to the dip observed in the $s$-wave $\pi \pi$ cross section around the $980\mathrm{MeV}$ coming from the interference of the $f_0(500)$ and $f_0(980)$ resonances. Its observation in coming upgrades of present facilities will shed light on the existence of these two resonances and their nature.

Comments: 7 pages, 4 figures