Double heavy tri-hadron bound state via delocalized π bond

The number of exotic candidates that are beyond the conventional quark model has increased dramatically over recent decades. Some of these can be viewed as analogues of the deuteron. Similarly, the existence of the triton indicates that bound states formed by three hadrons could also exist. To illustrate this possibility, we study the DD*K and BB*(K) over bar systems using the Born-Oppenheimer approximation. To leading order, only one-pion exchange potentials are considered. This means that the three constituents share one virtual pion. This is similar to the role of the delocalized pi bond for the formation of benzene in chemistry. After solving the Schrodinger equation, we find two three-body DD*K and BB*(K) over bar bound states with masses 4317.92(-4.32)( )(+3.66)MeV and 11013.65(-8.84)(+8.49) MeV, respectively. The masses of their DD*(K) over bar and B (B) over bar*(K) over bar analogues are 4317.92(-6.55)(+6.13) MeV and 11013.65(-9.02)(+8.68) MeV, respectively. From the experimental side, the D (D) over bar *K bound state could be found by analyzing the current world data on the B -> J/psi pi pi K process, by focusing on the J/psi pi K channel.