Towards exotic hidden-charm pentaquarks in QCD

Inspired by $P_c(4380)$ and $P_c(4450)$ recently observed by LHCb, a QCD sum rule investigation is performed, by which they can be identified as exotic hidden-charm pentaquarks composed of an anti-charmed meson and a charmed baryon. Our results suggest that $P_c(4380)$ and $P_c(4450)$ have quantum numbers $J^P=3/2^-$ and $5/2^+$, respectively. Furthermore, two extra hidden-charm pentaqurks with configurations $\bar{D}\Sigma_c^*$ and $\bar{D}^*\Sigma_c^*$ are predicted, which have spin-parity quantum numbers $J^P=3/2^-$ and $J^P=5/2^+$, respectively. As an important extension, the mass predictions of hidden-bottom pentaquarks are also given. Searches for these partners of $P_c(4380)$ and $P_c(4450)$ are especially accessible at future experiments like LHCb and BelleII.