The Z<sub>c</sub>(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.
The Z<sub>c</sub>(3900) is a decay product of the previously observed anomalous Y(4260) particle.
The Z<sub>c</sub>(3900) in turn decays into a charged pion () and a meson. This is consistent with the Z<sub>c</sub>(3900) containing four or more quarks.
The first evidence of the neutral Z<sub>c</sub>(3900) was provided by CLEO-c in 2013. It was later observed by BES III in 2015. It decays into a neutral pion () and a meson.
Researchers were expected to run decay experiments in 2013 to determine the particle's nature with more precision.