Heavy Quark Symmetry and Hidden Charm Pentaquarks

We report on the role of the heavy quark symmetry (HQS) in understanding the hidden charm pentaquarks, $P_c^+(4380)$ and $P_c^+(4450)$, observed by LHCb in $\Lambda_b^0 \to J/\psi\; p\; K^-$ decays, in the compact diquark-diquark-antiquark picture. In the HQS-limit, only the state $P_c^+(4450)$ is expected to be produced. Within this picture, we employ $SU(3)_F$ symmetry to discuss the mass spectrum and decays of the related pentaquark states $\bar{c}[cq][q^\prime q^{\prime\prime}]$ with $q, q^{\prime}, q^{\prime \prime} \in [u,d,s]$. Some of these pentaquarks are expected to be produced in $b$-baryon decays and we work out their relative decay widths