The Zc(3900) is a hadron, a type of subatomic particle made of quarks, believed to be the first tetraquark that has been observed experimentally.
The discovery was made in 2013 by two independent research groups: one using the BES III detector at the Chinese Beijing Electron Positron Collider, the other being part of the Belle experiment group at the Japanese KEK particle physics laboratory.
[1][2][3][4][5] The Zc(3900) is a decay product of the previously observed anomalous Y(4260) particle.
[6] The Zc(3900) in turn decays into a charged pion (π±) and a J/ψ meson.
[7] Researchers were expected to run decay experiments in 2013 to determine the particle's nature with more precision.