A new group of doubly charmed molecule with T-doublet charmed meson pair

Inspired by the observation of the doubly charmed tetraquark state $T_{cc}^+$ at the LHCb Collaboration, we systematically study the $S$-wave interactions between a pair of charmed mesons ($D_{1},\,D_{2}^{\ast}$) in the $T$-doublet, where we adopt the one-boson-exchange model and consider both the $S$-$D$ wave mixing and coupled channel effects. Our numerical results suggest that the prime doubly charmed molecular tetraquark candidates are the $S$-wave $D_1D_1$ state with $I(J^P)=0(1^+)$, the $S$-wave $D_1{D}_2^{\ast}$ states with $I(J^P)=0(1^+,\,2^+,\,3^+)$, and the $S$-wave ${D}_2^{\ast}{D}_2^{\ast}$ states with $I(J^P)=0(1^+,\,3^+)$. The $S$-wave $D_1D_1$ state with $I(J^P)=1(2^+)$, the $S$-wave $D_1{D}_2^{\ast}$ state with $I(J^P)=1(3^+)$, and the $S$-wave ${D}_2^{\ast}{D}_2^{\ast}$ state with $I(J^P)=1(4^+)$ may be the possible isovector doubly charmed molecular tetraquark candidates. We expect the experiments like the LHCb or Belle II collaborations to search for these predicted doubly charmed molecular tetraquarks near the $D_1D_1$, $D_1D_2^*$, and $D_2^*D_2^*$ thresholds in future.