摘要
The deuteron is a loosely bound state of two nucleons. It is natural to expect other bound states composed oftwo hadrons, that is, hadronic molecular states[1]. After the observation by the Belle Collaboration, the X(3872)was related to a loosely bound state of DˉD immediately due to the fact that its mass is near the DˉD threshold.Recently, the Belle Collaboration announced two charged bottomonium-like structures Zb(10610) and Zb(10650)near the BˉB and BˉB thresholds[2]. The analysis of the angular distribution indicated both Zb(10610) andZb(10650) favor IG(JP ) = 1+(1+). A structure Zc(3900) close to the DˉD threshold was also observed by theBESIII collaboration in the decay of Y(4260), Y(4260)!+??J= [3].
