Molecular tetraquarks and pentaquarks in chiral effective field theory

We studied the $D{\bar{D}}^{\ast }\mathrm{/}\bar{D}{D}^{\ast }$, $D^{\ast }{\bar{D}}^{\ast }$, ${\bar{D}}_s{D}^{\ast }\mathrm{/}{\bar{D}}_s^{\ast }D$, $B{\bar{B}}^{\ast }\mathrm{/}\bar{B}{B}^{\ast }$ and $B^{\ast }{\bar{B}}^{\ast }$ di-hadron interactions in chiral effective field theory ($\chi$EFT) up to the next-to-leading (NLO) order. The above-threshold tetraquark states $Z_c(3900)$, $Z_c(4020)$, $Z_{cs}(3985)$, $Z_b(10610)$, $Z_b(10650)$ can be explained as the corresponding di-hadron resonances, respectively. We also studied the ${\mathrm{\Sigma }}_c^{(\ast )}{\bar{D}}^{(\ast )}$ interactions to investigate the three hidden-charm pentaquarks $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$. We further used the parameters fixed from the $P_c$ states to predict the possible molecular states in ${\mathrm{\Xi }}_c{\bar{D}}^{(\ast )}$, ${\mathrm{\Xi }}_c^{\mathrm{\prime }}{\bar{D}}^{(\ast )}$ and ${\mathrm{\Xi }}_c^{\ast }{\bar{D}}^{(\ast )}$ systems. Our predictions of the ${\mathrm{\Xi }}_c{\bar{D}}^{(\ast )}$ bound states are very consistent with two new near-threshold structures recently observed by the LHCb Collaboration.