The strange partner of the $Z_c$ structures in a coupled-channels model

Abstract

The discovery of a new charged structure in the $K^{+}$ recoil-mass spectrum near the $D_s^{-}{D}^{\ast 0}/D_s^{\ast -}{D}^0$ threshold, dubbed $Z_{cs}(3985{)}^{-}$, reinforce the idea that the structure of hadrons goes beyond the naive $qqq$ and the $q\bar{q}$ structures. The existence of this state, with quark content $c\bar{c}s\bar{u}$, can be expected from the well-established $Z_c(3900{)}^{\pm }$ and $Z_c(4020)$ states using SU(3) flavor symmetry. The $Z_c$ structures have been explained using the chiral constituent quark model in a coupled-channels calculation and, in this work, we undertake the study of the $Z_{cs}(3985{)}^{-}$ using the same model. We are able to reproduce the $K^{+}$ recoil-mass spectrum without any fine tuning of the model parameters. The study of the analytical structure of the S-matrix allows us to conclude that the structure is due to the presence of one virtual pole. A second state, the SU(3) flavor partner of the $Z_c(4020)$ is predicted at $\sim 4110$ MeV/$c^2$. New states in the hidden bottom strange sector are also predicted.

Comments: 7 pages, 5 figures, 1 table. arXiv admin note: text overlap with arXiv:1808.00914