Abstract
The low-lying $S$-wave $QQ\bar{s}\bar{s}$ ($Q=c, b$) tetraquark states with $IJ^P=00^+$, $01^+$ and $02^+$ are systematically investigated in the framework of complex scaling range of chiral quark model. Every structure including meson-meson, diquark-antidiquark and K-type configurations, and all possible color channels in four-body sector are considered by means of a commonly extended variational approach, Gaussian expansion method. Several narrow and wide resonance states are obtained for $cc\bar{s}\bar{s}$ and $bb\bar{s}\bar{s}$ tetraquarks with $IJ^P=00^+$ and $02^+$. Meanwhile, narrow resonances for $cb\bar{s}\bar{s}$ tetraquarks are also found in $IJ^P=00^+$, $01^+$ and $02^+$ states. These results confirm the possibility of finding hadronic molecules with masses $\sim\,0.6\,\text{GeV}$ above the noninteracting hadron-hadron thresholds.
Highlights
We are witnessing in the last two decades of a big experimental effort for understanding the heavy-flavor quark sectors of both meson and baryon systems
The complex scaling method (CSM) applied to our chiral quark model has been already explained in Refs. [50,54]
Where the center-of-mass kinetic energy, TCM, is subtracted without loss of generality since we focus on the internal relative motions of quarks inside the multiquark system
Summary
We are witnessing in the last two decades of a big experimental effort for understanding the heavy-flavor quark sectors of both meson and baryon systems. The three newly announced hidden-charm pentaquarks, Pþc ð4312Þ, Pþc ð4440Þ, and Pþc ð4457Þ are favored to be molecular states of ΣcD Ã in, for instance, effective field theories [32,33], QCD sum rules [34], phenomenological potential models [35,36,37,38,39,40], heavy quark spin symmetry formalisms [41,42] and heavy hadron chiral perturbation theory [43]
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