$\bar{D}{\Sigma }_c^{\ast }$ and ${\bar{D}}^{\ast }{\Sigma }_c$ interactions and LHCb pentaquarks

Abstract

Recently, LHCb collaboration reported the observation of two hidden-charmed resonances $P_c(4380)$ and $P_c(4450)$ consistent with hidden-charmed pentaquarks. We perform a dynamical investigation about the $\bar{D}{\Sigma }_c^{\ast }(2520)$ and ${\bar{D}}^{\ast }{\Sigma }_c(2455)$ interactions which are described by the meson exchanges in a quasipotential Bethe-Salpeter equation approach. Two poles around $4450$ and $4390$ MeV are produced from the ${\bar{D}}^{\ast }{\Sigma }_c(2455)$ interaction with spin parities $3/2^{-}$ and $5/2^{+}$, respectively. The peak for $5/2^{+}$ state has a comparable hight as that of $3/2^{-}$ state in the $J/\psi p$ invariant mass spectrum. Another bound state with spin-parity $J^P=3/2^{-}$ is produced from the $\bar{D}{\Sigma }_c^{\ast }(2520)$ interaction. Such results suggest that the narrower LHCb pentaquark $P_c(4450)$ can be well interpreted as a $5/2^{+}$ ${\bar{D}}^{\ast }{\Sigma }_c(2455)$ molecular state while the $P_c(4380)$ is a $3/2^{-}$ ${\bar{D}}^{\ast }{\Sigma }_c(2455)$ molecular state mixed with other secondary origins.

Comments: Talk given at the 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto, July 2016