Hadronic molecules composed of a doubly charmed tetraquark state and a charmed meson

Abstract

The three pentaquark states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, discovered by the LHCb Collaboration in 2019, can be arranged into a complete heavy quark spin symmetry multiplet of hadronic molecules of ${\bar{D}}^{(\ast )}\hat{I}{\pounds }_c^{(\ast )}$. In the heavy quark mass limit, the $\hat{I}{\pounds }_c^{(\ast )}$ baryons can be related to the doubly charmed tetraquark states of isospin 1, i.e., $T_{\bar{c}\bar{c}}^{(\ast )}$( $T_{\bar{c}\bar{c}}^0$, $T_{\bar{c}\bar{c}}^1$, $T_{\bar{c}\bar{c}}^2$), via heavy antiquark diquark symmetry, which dictates that the ${\bar{D}}^{(\ast )}\hat{I}{\pounds }_c^{(\ast )}$ interactions are the same as the ${\bar{D}}^{(\ast )}{T}_{\bar{c}\bar{c}}^{(\ast )}$ interactions up to { heavy antiquark diquark symmetry} breakings. In this work, we employ the contact-range effective field theory to systematically study the ${\bar{D}}^{(\ast )}{T}_{\bar{c}\bar{c}}^{(\ast )}$ systems, and we show the existence of a complete heavy quark spin symmetry multiplet of hadronic molecules composed of a doubly charmed tetraquark state and a charmed meson. These are a new kind of hadronic molecules and, if discovered, can lead to a better understanding of the many exotic hadrons discovered so far. In addition, we summarise the triply charmed hexaquark states formed by different combinations of hadrons. In particular, we show that $\bar{\hat{I}}{\text{c◯}}_{ccc}p$ system can bind by the Coulomb force, which is analogous to a hydrogenlike atom.

accepted for publication in Eur.Phys.J.C