Manifestation of kaonium in the e+e−→K+K− process

We analyze the precise data obtained by the CMD-3 experiment on the ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into two charged kaons in the vicinity of the $\ensuremath{\phi}$ peak. A perfect fit is obtained only if a pole on the real axis below the reaction threshold is assumed. This can be interpreted as proof of the existence of the 2p state of kaonium, a compound of ${K}^{+}$ and ${K}^{\ensuremath{-}}$. The BABAR Collaboration data on the same process supports this conclusion and, in addition, points to the strong interaction as a dominant source of the binding energy. The possibility of discovering 2p kaonium in the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ process is discussed. The 2p state of ${K}^{0}$-onium is indicated on the basis of the CMD-3 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{L}^{0}$ data.