Pentaquarks with hidden charm as hadroquarkonia

Abstract We consider hidden charm pentaquarks as hadroquarkonium states in a QCD inspired approach. Pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. The LHCb $$P_c(4450)$$ Pc(4450) pentaquark is interpreted as a $$\psi '$$ ψ′ -nucleon bound state with spin-parity $$J^P=3/2^-$$ JP=3/2- . The partial decay width $$\varGamma (P_c(4450)\rightarrow J/\psi +N)\approx 11$$ Γ(Pc(4450)→J/ψ+N)≈11 MeV is calculated and turned out to be in agreement with the experimental data for $$P_c(4450)$$ Pc(4450) . The $$P_c(4450)$$ Pc(4450) pentaquark is predicted to be a member of one of the two almost degenerate hidden-charm baryon octets with spin-parities $$J^{P}=1/2^-,3/2^-$$ JP=1/2-,3/2- . The masses and decay widths of the octet pentaquarks are calculated. The widths are small and comparable with the width of the $$P_c(4450)$$ Pc(4450) pentaquark, and the masses of the octet pentaquarks satisfy the Gell-Mann–Okubo relation. Interpretation of pentaquarks as loosely bound $$\varSigma _c\bar{D}^*$$ ΣcD¯∗ and $$\varSigma _c^*\bar{D}^*$$ Σc∗D¯∗ deuteronlike states is also considered. We determine quantum numbers of these bound states and calculate their masses in the one-pion exchange scenario. The hadroquarkonium and molecular approaches to exotic hadrons are compared and the relative advantages and drawbacks of each approach are discussed