Pion-induced production of the $Z_c(3900)$ off a nuclear target

TL;DR

This paper explores the production of the exotic state Z_c(3900) via pion beams on nuclear targets, predicting significantly higher cross sections compared to proton targets, and suggests experimental investigation at facilities like COMPASS and J-PARC.

Contribution

It introduces a method to produce Z_c(3900) using pion-induced reactions on nuclear targets, with detailed cross section calculations showing enhanced production rates.

Findings

Cross sections on nuclear targets are about 100 times larger than on protons.

Predicted cross sections are approximately 100 nb for nuclear targets.

Experimental feasibility at facilities like COMPASS and J-PARC is suggested.

Abstract

We investigate the possibility to study the charmoniumlike state $Z_c(3900)$ through the pion-induced production off a nuclear target. By using a high-energy pion beam, the $Z_c(3900)$ can be produced off a proton or nucleus though the Primakoff effect. The production amplitude is calculated in an effective Lagrangian approach combined with the vector dominance model. The total cross sections of the $p(\pi^-, Z^-_c(3900))$ and $p(\pi^-, Z^-_c(3900)\to J/\psi\pi^-)$ reactions are calculated, and their order of magnitude is about 0.1 and 0.01nb, respectively, with an assumption of branch ratio 10\% for the $Z_c(3900)$ decay in $J/\psi\pi$ channel. If the proton target is replaced by a nuclear target, the production of the $Z_c(3900)$ enhances obviously. The predicted total cross sections for the $A(\pi^-, Z^-_c(3900))$ and $A(\pi^-, Z^-_c(3900)\to J/\psi\pi^-)$ reactions with $A=^{12}$C or $^{208}$Pb are on the order of magnitude of 100 and 10 nb, respectively, which is about one thousand times larger than the cross sections off a proton target. Based on these the results, we suggest the experimental study of the $Z_c(3900)$ by using high-energy pion beams with a nuclear target at facilities such as COMPASS and J-PARC.