Molecular tetraquarks and pentaquarks in chiral effective field theory

Abstract: We studied the $D\bar{D}^\ast/\bar{D}D^\ast$, $D^\ast\bar{D}^\ast$, $\bar{D}s D^\ast/\bar{D}_s^\ast D$, $B\bar{B}^\ast/\bar{B}B^\ast$ 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 $\Sigma_c^{(\ast)}\bar{D}^{(\ast)}$ 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 $\Xi_c\bar{D}^{(\ast)}$, $\Xi_c^\prime\bar{D}^{(\ast)}$ and $\Xi_c^\ast\bar{D}^{(\ast)}$ systems. Our predictions of the $\Xi_c\bar{D}^{(\ast)}$ bound states are very consistent with two new near-threshold structures recently observed by the LHCb Collaboration.