Mass spectra of full-heavy and double-heavy tetraquark states in the conventional quark model

Abstract

A comprehensive study of the S-wave heavy tetraquark states with identical quarks and antiquarks, specifically QQQ¯′Q¯′ (Q,Q′=c, b), QQs¯s¯/Q¯Q¯ss, and QQq¯q¯/Q¯Q¯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 QQq¯q¯ states with the isospin and spin-parity quantum numbers I(JP)=0(1+): two bound bbq¯q¯ states with the binding energies, 153 MeV and 4 MeV below the BB* threshold, and a shallow ccq¯q¯ state at −15 MeV from the DD* threshold. The deeper bbq¯q¯ bound state aligns with the lattice QCD predictions, while ccq¯q¯ bound state, still has a much larger binding energy than the recently observed Tcc+ by LHCb collaboration. No bound states are identified for the QQQ¯′Q¯′, QQs¯s¯, and QQq¯q¯ with I=1. Our analysis shows that the bound QQQ¯′Q¯′ states are more probable with a larger mass ratio, mQ/mQ′. Experimental investigation for these states is desired, which will enrich our understanding of hadron spectroscopy and probe insights into the confinement mechanisms within tetraquarks. Published by the American Physical Society 2025