The newly observed $ Z_{cs}(3985)^- $ state: in vacuum and a dense medium

TL;DR

This paper studies the properties of the newly observed $Z_{cs}(3985)^-$ state, estimating its mass in vacuum and dense media, and explores its relation to similar states, providing predictions for future experimental verification.

Contribution

It offers the first theoretical estimates of the $Z_{cs}(3985)^-$ mass in vacuum and dense media, and predicts properties of its b-partner $Z_{bs}$, enhancing understanding of exotic hadrons.

Findings

The vacuum mass estimate agrees with experimental data.

Mass and coupling parameters vary linearly with medium density.

Predicted $Z_{bs}$ mass is approximately 10732 MeV.

Abstract

We report on some properties of the newly observed charged hidden-charmed open strange $ Z_{cs}(3985)^- $ state by BESIII Collaboration. Assigning the quantum numbers $ J^{P} = 1^{+}$ and the quark composition $ c \bar c s\bar u $ and considering it as the strange partner of the famous $ Z_c(3900) $ state, we estimate the mass of the $ Z_{cs}(3985)^- $ resonance in vacuum and compare it with the experimental data. We also investigate its mass, current coupling and vector-self energy in a medium with finite density. Our result on the mass in vacuum agrees well with the experimental data. We estimate the mass and current coupling of the b-partner of this state, $ Z_{bs}$, in the vacuum as well. For its mass we get $ m_{Z_{bs}}= 10732^{+97}_{-46}~\mbox{MeV}$, which may be checked via other nonperturbative approaches as well as future experiments. We present the dependence of the spectroscopic parameters of $ Z_{cs}(3985)^- $ state on density and observe that these parameters are linearly changed with increasing in the density.