Hadronic molecules with four charm or beauty quarks

We apply the extended local hidden gauge formalism to study the meson-meson interactions with the quark constituents cc c c, cc c b/ c c cb, cc b b/ c c bb, bb c b/ b b cb, and bb b b, where the exchanged mesons can only be the fully-heavy vector mesons J/, Bc^*, and. We solve the coupled-channel Bethe-Salpeter equation to derive two poles in the bb c b system and two poles in the cc c b system (with four charge-conjugated poles in the b b cb and c c cb systems): one pole existing in the bb c b system corresponds to the sub-threshold bound state when setting the cutoff momentum > 850 MeV, while it causes the threshold effect with 1100 MeV; the two poles existing in the cc c b system correspond to the sub-threshold bound states only when setting > 1550 MeV and > 2650 MeV, making them difficult to be identified as deeply-bound hadronic molecules. We propose to investigate the two poles of the bb c b system in the ^+^-Bc^- channel at LHC.