Observation of the Exotic State ${\pi }_1(1600)$ in $\psi (2S)\to \gamma {\chi }_{c1},{\chi }_{c1}\to {\pi }^{+}{\pi }^{-}{\eta }^{\prime }$

BESIII Collaboration, M. Ablikim, M. N. Achasov +750

A partial wave analysis of the process $\psi (2S)\to \gamma {\chi }_{c1},{\chi }_{c1}\to {\pi }^{+}{\pi }^{-}{\eta }^{\prime }$ is performed using $(2712.4\pm 14.3)\times 10^6$ $\psi (2S)$ events collected with t…