Abstract
The study of medium effects on properties of particles embedded in nuclear matter is of great importance for understanding the nature and internal quark-gluon organization as well as exact determination of the quantum numbers, especially of the exotic states. In this context, we study the physical properties of one of the famous charmonium-like states, $Z_c(3900)$, in a cold dense matter. We investigate the possible shifts in the mass and current-meson coupling of the $Z_c(3900)$ state due to the dense medium at saturation density, $ \rho^{sat} $, by means of the in-medium sum rules. We also estimate the vector self-energy of this state at saturation nuclear matter density. We discuss the behavior of the spectroscopic parameters of this state with respect to the density up to a high density corresponding to the core of neutron stars, $\rho\approx 5\rho^{sat}$. Both the mass and current-coupling of this state show nonlinear behavior and decrease with respect to the density of the medium: the mass reaches roughly $30\%$ of its vacuum value at $ \rho=5\rho^{sat} $, while the current-coupling approaches zero at $ \rho\approx2.1\rho^{sat} $, when the central values of the auxiliary and other input parameters are used.
Highlights
The standard hadrons are divided into qqand qqq=qq ̄ qsystems
The study of medium effects on properties of particles embedded in nuclear matter is of great importance for understanding the nature and internal quark-gluon organization as well as exact determination of the quantum numbers, especially of the exotic states
We investigate the effects of a dense medium on the parameters of the Zcð3900Þ state and look for the behavior of the mass, current-meson coupling, and vector self-energy of this charmoniumlike state, considering it as a compact tetraquark state
Summary
The standard hadrons are divided into qqand qqq=qq ̄ qsystems. Neither the quark model nor the QCD excludes the existence of the structures out of these configurations. We have made good progress in the determination of different aspects of these states in theory. Most of the discovered exotic states are tetraquarks of the XYZ family. The XYZ states are the charmoniumlike or bottomoniumlike resonances, which, because of their mass, cannot be placed in the charmonium or bottomonium picture: These resonances, mainly with QQqqquark content, have different properties than the standard excited quarkonium states. Many XYZ states have been observed by the Belle, BESIII, BABAR, LHCb, CMS, D0, CDF, and CLEO-c collaborations [1], and their masses, widths and quantum numbers JPC have been predicted. Detailed analysis of the experimental status of these states and various theoretical models can be found in numerous new review articles [2,3,4,5]
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