Studying the scalar bound states of KK system in Bethe-Salpeter formalism

We study the possible bound states of the K (K) over bar system in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. We find that the bound states exist. However, these bound states have very small decay widths. Therefore, besides the possible K (K) over bar component, there may be some other structures in the observed f(0)(980) and a(0)(980).