Heavy quark symmetry and weak decays of the $b$-baryons in pentaquarks with a $c\bar{c}$ component

Understand

The discovery of the baryonic states $P_c^+(4380)$ and $P_c^+(4450)$ by the LHCb collaboration has evoked a lot of theoretical interest.

• These states have the minimal quark content $c \bar{c} u u d$.
• Interpreted as hidden charm diquark-diquark-antiquark baryons, the assigned spin and angular momentum quantum numbers are $P_c^+(4380)= \{\bar{c} [cu]_{s=1} [ud]_{s=1}; L_{\mathcal{P}}=0, J^{\rm P}=\frac{3}{2}^- \}$ and $P_c^+(4450)= \{\bar{c} [cu]_{s=1} [ud]_{s=0}; L_{\mathcal{P}}=1, J^{\rm P}=\frac{5}{2}^+ \}$, where $s=0,1$ are the spins of the diquarks and $L_{\mathcal{P}}=0,1$ are the orbital angular momentum quantum numbers of the pentaquarks.
• We point out that heavy quark symmetry allows only the higher mass pentaquark state $P_c^+(4450)$ having $[ud]_{s=0}$ to be produced in $\Lambda_b^0$ decays, whereas the lower mass state $P_c^+(4380)$ having $[ud]_{s=1}$ is disfavored.