Triply heavy tetraquark states

Abstract

In the framework of an extended chromomagnetic model, we systematically study the mass spectrum of the S-wave qQQ¯Q¯ tetraquarks. Their mass spectra are mainly determined by the color interaction. For the qcc¯c¯, qbc¯c¯, and qbb¯b¯ tetraquarks, the color interaction favors the color-sextet |(qQ)6c(Q¯Q¯)6¯c configuration over the color-triplet |(qQ)3¯c(Q¯Q¯)3c one. But for the qcb¯b¯ tetraquarks, the color-triplet configuration is favored. We find no stable states which lie below the thresholds of two pseudoscalar mesons. The lowest axial-vector states with the qQb¯b¯ flavor configuration may be narrow. They lie just above the thresholds of two pseudoscalar mesons, but cannot decay into these channels because of the conservation of the angular momentum and parity.