Experimental constraints on the properties of $P_c$ states

Abstract

Using new experimental data on photoproduction and ${\Lambda }_b^0$ decays, we derive constraints on the properties of the LHCb $P_c$ states. We conclude that $P_c(4312)$, $P_c(4380)$ and $P_c(4440)$ can be described as ${\Sigma }_c\bar{D}$, ${\Sigma }_c^{\ast }\bar{D}$ and ${\Sigma }_c{\bar{D}}^{\ast }$ molecules, but that $P_c(4457)$ does not fit into the same picture. Based on the apparent absence of additional partner states, and the striking disparity between ${\Lambda }_c^{+}{\bar{D}}^0$ and ${\Lambda }_c^{+}{\bar{D}}^{\ast 0}$ decays, we conclude that $P_c(4440)$ has $3/2^{-}$ quantum numbers. Using heavy-quark symmetry we predict large experimental signals for $P_c$ states in ${\eta }_{c}p{K}^{-}$, ${\Lambda }_c^{+}{\bar{D}}^{\ast 0}{K}^{-}$, and ${\Sigma }_c^{(\ast )}\bar{D}{K}^{-}$. We also argue that current experimental data on photoproduction is almost at the level of sensitivity required to observe $P_c$ states.

Comments: 27 pages, 4 figures, minor revisions for journal