Study of possible molecular states of Ds (∗) Ds (∗) and Bs (∗) Bs (∗)

Recently the LHCb Collaboration reported a new exotic state Tcc+ which is conjectured to be a molecular state of D0D∗+ (or D∗0D+) theoretically. Belle Collaboration also searched for tetraquark state Xccss in DsDs (Ds∗Ds∗) final states but no significant signals were observed, which did not rule out the existence of Xccss as a molecular state of DsDs (Ds∗Ds∗). Inspired by these experimental results on double charmed exotic state, in this paper we study whether the molecular bound states of Ds(∗)Ds(∗) and Bs(∗)Bs(∗) can exist 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 Bs∗ 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