Observation of the $X(1840)$ at BESIII

Jingqing Zhang

Observation of the $X(1840)$ in the $3({\pi }^{+}{\pi }^{-})$ invariant mass in $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$ at BESIII is reviewed. With a sample of $225.3\times 10^6$ $J/\psi$ events collected with t…