Evidence for the Cusp Effect in ${\eta }^{\prime }$ Decays into $\eta {\pi }^0{\pi }^0$

BESIII Collaboration, M. Ablikim, M. N. Achasov +560

Using a sample of $4.3\times 10^5$ ${\eta }^{\prime }\to \eta {\pi }^0{\pi }^0$ events selected from the ten billion $J/\psi$ event dataset collected with the BESIII detector, we study the decay ${\eta }^{\prime }\to \eta {\pi }^0{\pi }^0$ wit…