First observation of the M1 transition $\psi (3686)\to \gamma {\eta }_c(2S)$

M. Ablikim, M. N. Achasov, D. J. Ambrose +356

Using a sample of 106 million ψ(3686) events collected with the BESIII detector at the BEPCII storage ring, we have made the first measurement of the M1 transition between the radi…