A meson-baryon molecular interpretation for some $\hat{I}{\text{c◯}}_c$ excited baryons

Abstract

We explore the possibility that some of the five narrow $\hat{I}{\text{c◯}}_c$ resonances recently observed at LHCb could correspond to pentaquark states, structured as meson-baryon bound states or molecules. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm $+1$, strangeness $-2$ and isospin 0 sector is built from t-channel vector meson exchange, using effective Lagrangians. The resulting s-wave coupled-channel unitarized amplitudes show the presence of two structures with similar masses and widths to those of the observed $\hat{I}{\text{c◯}}_c(3050{)}^0$ and $\hat{I}{\text{c◯}}_c(3090{)}^0$. The identification of these resonances with the meson-baryon bound states found in this work would also imply assigning the values $1/2^{-}$ for their spin-parity. An experimental determination of the spin-parity of the $\hat{I}{\text{c◯}}_c(3090{)}^0$ would help in disentangling its structure, as the quark-based models predict its spin-parity to be either $3/2^{-}$ or $5/2^{-}$.

9 pages, 4 figures