Search for the weak decay ${\eta }^{\prime }\to K^{\pm }{\pi }^{\mp }$ and precise measurement of the branching fraction $\mathcal{B}(J/\psi \to \varphi {\eta }^{\prime })$

BESIII Collaboration, M. Ablikim, M. N. Achasov +414

We present the first search for the rare decay of ${\eta }^{\prime }$ into $K^{\pm }{\pi }^{\mp }$ in $J/\psi \to \varphi {\eta }^{\prime }$, using a sample of $1.3\times 10^9$ $J/\psi$ events collected with the BESII…