Experimental constraints on the properties of P_c states

Using new experimental data on photoproduction and Λ _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 Σ _cD̅ , Σ _c^*D̅ and Σ _cD̅^* 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 Λ _c^+D̅^0 and Λ _c^+D̅^*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 η _c p K^- , Λ _c^+D̅^*0K^- , and Σ _c^(*)D̅K^- . We also argue that current experimental data on photoproduction is almost at the level of sensitivity required to observe P_c states.