Combined analysis of the Zc (3900) and the Zcs (3985) exotic states

Abstract

We have performed a combined analysis of the BESIII data for both the Zc(3900) and Zcs(3985) structures, assuming that the latter is an SU(3) flavor partner of the former one. We have improved on the previous analysis of Albaladejo et al. [Phys. Lett. B 755, 337 (2016)PYLBAJ0370-269310.1016/j.physletb.2016.02.025] by computing the amplitude for the D1D¯D∗ triangle diagram considering both D- and S-wave D1D∗π couplings. We have also investigated effects from SU(3) light-flavor violations, which are found to be moderate and of the order of 20%. The successful reproduction of the BESIII spectra, in both the hidden-charm and hidden-charm strange sectors, strongly supports that the Zcs(3985) and Zc(3900) are SU(3) flavor partners placed in the same octet multiplet. The best results are obtained when an energy-dependent term in the diagonal D(∗)D¯(s)(∗) interaction is included, leading to resonances (poles above the thresholds) to describe these exotic states. We have also made predictions for the isovector Zc∗ and isodoublet Zcs∗, D∗D¯∗, and D∗D¯s∗ molecules, with JPC=1+- and JP=1+, respectively. These states would be heavy-quark spin symmetry (HQSS) partners of the Zc and Zcs. Besides the determination of the masses and widths of the Zc(3900) and Zcs(3985), we also predict those of the Zc∗ and Zcs∗ resonances.