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

Abstract

We report on some properties of the newly observed charged hidden-charmed open strange $$ Z_{cs}(3985)^- $$ Z cs ( 3985 ) - state by BESIII Collaboration. Assigning the quantum numbers $$ J^{P} = 1^{+}$$ J P = 1 + and the quark composition $$ c \bar{c} s\bar{u} $$ c c ¯ s u ¯ and considering it as the strange partner of the famous $$ Z_c(3900) $$ Z c ( 3900 ) state, we estimate the mass of the $$ Z_{cs}(3985)^- $$ 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, $$ Z_{bs}$$ Z bs , in the vacuum as well. For its mass we get $$ m_{Z_{bs}}= 10732^{+97}_{-46}~\hbox {MeV}$$ m Z bs = 10732 - 46 + 97 MeV , which may be checked via other nonperturbative approaches as well as future experiments. We present the dependence of the spectroscopic parameters of $$ Z_{cs}(3985)^- $$ Z cs ( 3985 ) - state on density and observe that these parameters are linearly changed with increasing in the density.

The new $P_{\rm c}(4337)$, $P_{\rm cs}(4459)$, $Z_{\rm cs}(3985)$ and $Z_{\rm cs}(4003)$ and the possible emergence of flavor pentaquark octets and tetraquark nonets

“…[18][19][20][21] on the pentaquark case and those of Refs. [22][23][24][25][26][27][28][29][30] on the Z cs tetraquarks. The experimental observation of emerging pentaquark octets and tetraquark nonets might be one of the keys to discriminate among the different interpretations available for tetra-and pentaquarks * Electronic address: santopinto@ge.infn.it [4,6,8,30,31].…”

The $Z_{cs}(3985)$ structure, if a triangle/kinematic singularity, would disappear when heated in Heavy Ion Collisons.

“…The community of hadron spectroscopy has been busy trying to ascertain whether it accepts a multiquark interpretation [6], whether one can expect a molecular composition [7], or whether threshold and/or triangle production effects [8] are at play and no new hadron is expected. To bring future heavyion collision data to bear, we point out in this contribution that the threshold/triangle kinematic coincidences are destroyed by the finite-temperature medium, whereas a real hadron is expected to continue existing in the medium though its mass is expected to drop perhaps 10% at the finite temperature just below the phase transition between the quark-gluon plasma and the hadron gas [9], and similarly at finite density [10].…”

Strange hidden-charm tetraquarks in constituent quark model

“…Besides, it is the first candidate of the charged hidden-charm tetraquark state with strangeness, whose discovery can provide more hints to the quest of charged exotic Z structures. Therefore, the observation of Z cs (3985) − immediately stimulated a lot of theoretical discussions [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”