Study of possible molecular states of D?? ,D?, and B? ,B?

Recently the LHCb Collaboration reported a new exotic state T??cc which is conjectured to be a molecular DsDs (D???sD???s) final states but no significant signals were observed, which did not rule out the existence of Xccss as a molecular state of DsDs (D???sD???s). Inspired by these experimental results on double charmed exotic state, in this paper we study whether the molecular bound states of D??????? with the Bethe-Salpeter (BS) equation approach. We employ heavy meson chiral perturbation theory and one-boson-exchange approximation to calculate the interaction kernels in the BS equations. Our numerical results suggest that two B???s mesons perhaps form a 0?? molecular state. Future experimental search for Xccss and Xbbss states in other decay channels may shed light on the structure of double charmed exotic state.