Hidden-charm and hidden-bottom molecular pentaquarks in chiral perturbation theory

Understand

The newly observed $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ at the LHCb experiment are very close to the $\Sigma_c\bar{D}$ and $\Sigma_c\bar{D}^\ast$ thresholds.

• In this work, we perform a systematic study and give a complete picture on the interactions between $\Sigma_c^{(\ast)}$ and $\bar{D}^{(\ast)}$ systems in the framework of heavy hadron chiral perturbation theory, where the short-range contact interaction, long-range one-pion-exchange contribution, and intermediate-range two-pion-exchange loop diagrams are all considered.
• We first investigate the three $P_c$ states without and with considering the $\Lambda_c$ contribution in the loop diagrams.
• It is difficult to simultaneously reproduce the three $P_c$s unless the effect of $\Lambda_c$ is included.