Narrow Results

In this paper, we restudy the ground state mass spectrum of the diquark–diquark–antiquark-type $uudc\bar{c}$ pentaquark states with the QCD sum rules by carrying out the operator product expansion up to the vacuum condensates of dimension 13 in a consistent way. The predicted masses support assigning the $P_c(4312)$ to be the hidden-charm pentaquark state with $J^P={\frac{1}{2}}^{-}$, assigning the $P_c(4440)$ to be the hidden-charm pentaquark state with $J^P={\frac{1}{2}}^{-}$, ${\frac{3}{2}}^{-}$ or ${\frac{5}{2}}^{-}$, assigning the $P_c(4457)$ to be the hidden-charm pentaquark state with $J^P={\frac{1}{2}}^{-}$ or ${\frac{3}{2}}^{-}$.

In this paper, we study the scalar-diquark–scalar-diquark–antiquark-type $udsc\bar{c}$ pentaquark state with the QCD sum rules, the predicted mass $M_P=4.47\pm 0.11\mathrm{\text{GeV}}$ is in excellent agreement with the experimental data $4458.8\pm 2.9_{-1.1}^{+4.7}\mathrm{\text{MeV}}$ from the LHCb collaboration, and supports assigning the $P_{cs}(4459)$ to be the hidden-charm pentaquark state with the spin-parity $J^P={\frac{1}{2}}^{-}$. We take into account the flavor $SU(3)$ mass-breaking effect, and estimate the mass spectrum of the diquark–diquark–antiquark-type $udsc\bar{c}$ pentaquark states with the strangeness $S=-1$.

The first two pentaquark candidates P_c(4380) and P_c(4450) were observed by LHCb Collaboration in 2015. Recently, they presented their improved measurements in the P_c energy range, that a new narrow signal denoted as P_c(4312) is reported and the previous observed structure P_c(4450) is resolved into two narrow states, P_c(4440) and P_c(4457) while there is no obvious signal for the broad state P_c(4380). We analyze the strong decays of these P_c states systematically in the hadronic molecule pictures. With the effective Lagrangian method, the partial widths of these P_c decaying into all allowed channels are estimated. Our results show that these P_c states are good candidates of the S-wave $\overline{D}{\mathrm{\Sigma }}_c,\overline{D}{\mathrm{\Sigma }}_c^{*}$ and $\overline{D}*{\mathrm{\Sigma }}_c$ molecules. Also other possible flavor and spin partners of P_c states are investigated in the present work.

We adopt the chiral perturbation theory to calculate the ${\displaystyle {\sum }_c^{(*)}{\overline{D}}^{(*)}}$ interaction to the next-to-leading order (NLO) and include the couple-channel effect in the loop diagrams. We reproduce the three P_c states in the molecular picture after including the ${\mathrm{\Lambda }}_c{\overline{D}}^{(*)}$ intermediate states. We also discuss some novel observations arising from the loop diagrams.