Photon-induced production of the exotic charged charmonium-like state $Z_c(3900)$ off nuclear targets and its internal structure

TL;DR

This study explores how photon-induced reactions on nuclear targets can reveal the internal structure of the exotic $Z_c(3900)$ state, using a collision model to compare different structural hypotheses and predict measurable observables.

Contribution

It introduces a comprehensive model to analyze $Z_c(3900)$ production off nuclei, considering various internal structure scenarios and predicting observables sensitive to these structures.

Findings

Observables show sensitivity to the $Z_c(3900)$ internal structure.

Predicted cross sections vary with target nucleus and energy.

Results can guide future experimental investigations.

Abstract

In this paper, we investigate the possibility to study the famous charged charmonium-like state $Z_c(3900)$ production off nuclear targets and its properties in inclusive photon-induced reactions near the kinematic threshold within the collision model based on the nuclear spectral function. The model accounts for its charged components $Z_c(3900)^{\pm}$ production in direct photon-nucleon interactions as well as three different popular scenarios for their internal structures: compact tetraquarks, molecules of the two open-charm mesons and mixtures of both of them. We calculate the absolute and relative excitation functions for production of $Z_c(3900)^{\pm}$ mesons on $^{12}$C and $^{184}$W target nuclei at initial photon energies of 9.0-17.5 GeV, the absolute momentum differential cross sections and their ratios for the $Z_c(3900)^{\pm}$ production off these target nuclei at laboratory polar angles of 0$^{\circ}$-10$^{\circ}$ and at photon energy of 14 GeV as well as the A-dependences of the ratios of the total cross sections for $Z_c(3900)^{\pm}$ production at photon energy of 14 GeV within the adopted scenarios for the $Z_c(3900)^{\pm}$ internal structures. We demonstrate that the absolute and relative observables considered show a certain sensitivity to the $Z_c(3900)^{\pm}$ internal structures which are by far the best known. Hence, they might be useful for the determination of these structures -- the issue which has attracted much attention in the hadron physics community -- from the comparison of them with the experimental data from the future high-precision experiments at the CEBAF facility.