The researchers explored the DD* and BB* interactions in the Bethe-Salpter equation approach, which contributes to understanding the Zc（3900）observed at BESIII recently.
It is the most interesting topic in hadron physics to search for the new hadron state which is beyond the conventional quark model. The hadronic molecular state is a loosely bound state of two hadrons through the interaction between them. The masses of the Zc(3900) observed at BESIII and the Zb(10610) observed at Belle stand near the thresholds of DD* and BB*, which suggests Zc(3900) and Zb(10610) may be molecular state.
The researchers proposed the theoretical method of using the Bethe-Salpeter equation to study the molecular states (see Fig.1), for the reason that it was found that there exist serious problems in the widely used one-boson-exchange model when one applied the model to a system composed of two constituents with different masses and/or spins. With this method, we studied the DD* and BB* interactions. The results showed that there is no bound state from the DD* and BB* interactions, which is consistent with the Lattice QCD. Hence, the molecular state explanations of the Zc(3900) and the Zb(10610) can be excluded in the current theoretical frame.
The results have been published in Phys. Rev. D90: 076008 (2014)
The article can be linked as follows:
Fig.1 The diagram for the Bethe-Salpeter equation