Possible S-wave Bound-States of Two Pseudoscalar Mesons
  Using the potentials derived from vector-meson-exchanges, the $K\bar K$, $DK$, $B\bar K$, $D\bar D$, $B\bar B$, $BD$, $\bar D K$, $BK$ and $B\bar D$ systems are studied. Possible S-wave bound-states of two pseudoscalar mesons are discussed. We find that systems of $DB$, $D\bar D$, $B\bar B$ and $DK$ with isospin 0 are likely to form S-wave bound states via strong interactions while the others are unlikely to be bound by the strong interaction sector alone. With the Coulomb potential, the $K^+K^-$ system can form an atomic bound state - the kaonium. The influence of the one-meson-exchange potential on the ground state energy of the kaonium and its decay widths to $\pi\pi$ and $\pi\eta$ are evaluated. 
Yin-Jie Zhang, Huan-Ching Chiang, Peng-Nian Shen and Bing-Song Zou