In the framework of the chiral quark model along with complex scaling range, we perform a dynamical study on the low-lying $S$-wave double-heavy tetraquark states ($QQ\overline{q}\overline{q}$, $Q=c$, $b$ and $q=u$, $d$) with an accurate computing approach, Gaussian expansion method. The meson-meson and diquark-antidiquark configurations within all possible color structures for spin-parity quantum numbers $J^P=0^{+}$, $1^{+}$, and $2^{+}$ and in the 0 and 1 isospin sectors are considered. Possible tightly bound and narrow resonance states are obtained for double-charm and double-bottom tetraquarks with $I{J}^P=01^{+}$, and these exotic states are also obtained in charm-bottom tetraquarks with $00^{+}$ and $01^{+}$ quantum numbers. Only a loosely bound state is found in charm-bottom tetraquarks of $02^{+}$ states. All of these bound states within meson-meson configurations are loosely bound whether in color-singlet channels or coupling to hidden-color ones. However, compact structures are available in diquark-antidiquark channels except for charm-bottom tetraquarks in $02^{+}$ states.

• Received 10 November 2019

DOI:https://doi.org/10.1103/PhysRevD.101.014001

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Published by the American Physical Society