From tetraquarks to hexaquarks: A systematic study of heavy exotics in the largeNclimit

A systematic study of multiquark exotics with one or ${\mathit{N}}_{\mathit{c}}$-1 heavy quarks in the large ${\mathit{N}}_{\mathit{c}}$ limit is presented. By binding a chiral soliton to a heavy meson, either a normal ${\mathit{N}}_{\mathit{c}}$-quark baryon or an exotic (${\mathit{N}}_{\mathit{c}}$+2)-quark baryon is obtained. By replacing the heavy quark with ${\mathit{N}}_{\mathit{c}}$-1 heavy antiquarks, exotic (2${\mathit{N}}_{\mathit{c}}$-2)-quark and 2${\mathit{N}}_{\mathit{c}}$-quark mesons are obtained. When ${\mathit{N}}_{\mathit{c}}$=3, they are just the normal triquark baryon Qqq, the exotic pentatquark baryon Qq¯ q¯ q¯ q¯, tetraquark dimeson Q¯ Q¯qq, and the hexaquark dibaryon Q¯ Q¯q¯ q¯ q¯ q¯, respectively. Their stabilities and decays are also discussed. In particular, it is shown that the ‘‘heavy to heavy’’ semileptonic decays are described by the Isgur-Wise form factors of the normal baryons.