Mass Spectra of Full-Heavy and Double-Heavy Tetraquark States in the Conventional Quark Model

A comprehensive study of the S-wave heavy tetraquark states with identical quarks and antiquarks, specifically QQQ̅'Q̅' (Q, Q'=c,b), QQs̅s̅/Q̅Q̅ ss, and QQq̅q̅/Q̅Q̅ qq (q=u,d), are studied in a unified constituent quark model. This model contains the one-gluon exchange and confinement potentials. The latter is modeled as the sum of all two-body linear potentials. We employ the Gaussian expansion method to solve the full four-body Schrödinger equations, and search bound and resonant states using the complex-scaling method. We then identify 3 bound and 62 resonant states. The bound states are all QQq̅q̅ states with the isospin and spin-parity quantum numbers I(J^P)=0(1^+): two bound bbq̅q̅ states with the binding energies, 153 MeV and 4 MeV below the BB^* threshold, and a shallow ccq̅q̅ state at -15 MeV from the DD^* threshold. The deeper bbq̅q̅ bound state aligns with the lattice QCD predictions, while ccq̅q̅ bound state, still has a much larger binding energy than the recently observed T^+_cc by LHCb collaboration. No bound states are identified for the QQQ̅'Q̅', QQs̅s̅ and QQq̅q̅ with I=1. Our analysis shows that the bound QQQ̅'Q̅' states are more probable with a larger mass ratio, m_Q/m_Q'. Experimental investigation for these states is desired, which will enrich our understanding of hadron spectroscopy and probe insights into the confinement mechanisms within tetraquarks.