Manifestation of kaonium in the $e^+e^- \to K^+K^-$ process

Abstract

We analyze the precise data obtained by the CMD-3 experiment on the $e^+e^-$ annihilation into two charged kaons in the vicinity of the $\phi$ 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 $K^-$. 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 $e^+e^-\rightarrow \pi^+\pi^-$ process is discussed. The 2p state of $K^0$-onium is indicated on the basis of the CMD-3 $e^+e^-\rightarrow K^0_SK^0_L$ data.