Coupled-channel analysis of the possible $D^{(*)}D^{(*)}$, $\bar{B}^{(*)}\bar{B}^{(*)}$ and $D^{(*)}\bar{B}^{(*)}$ molecular states

Abstract: We perform a coupled-channel study of the possible deuteron-like molecules with two heavy flavor quarks, including the systems of $D^{()}D^{()}$ with double charm, $\bar{B}^{()}\bar{B}^{()}$ with double bottom and $D^{()}\bar{B}^{()}$ with both charm and bottom, within the one-boson-exchange model. In our study, we take into account the S-D mixing which plays an important role in the formation of the loosely bound deuteron, and particularly, the coupled-channel effect in the flavor space. According to our calculation, the states $D^{()}D^{()}[I(J^P)=0(1^+)]$ and $(D^{()}D^{()})_s[J^P=1^+]$ with double charm, the states $\bar{B}^{()}\bar{B}^{()}[I(J^P)=0(1^+),0(2^+),1(0^+),1(1^+),1(2^+)]$, $(\bar{B}^{()}\bar{B}^{()})_s[J^P=0^+,1^+,2^+]$ and $(\bar{B}^{()}\bar{B}^{()})_{ss}[J^P=0^+,1^+,2^+]$ with double bottom, and the states $D^{()}\bar{B}^{()}[I(J^P)=0(0^+),0(1^+)]$ and $(D^{()}\bar{B}^{()})_s[J^P=0^+,1^+]$ with both charm and bottom are good molecule candidates. However, the existence of the states $D^{()}D^{()}[I(J^P)=0(2^+)]$ with double charm and $D^{()}\bar{B}^{()}[I(J^P)=1(1^+)]$ with both charm and bottom is ruled out.