Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is the exotic $X(5568)$ a bound state?   Stimulated by the recent observation of the exotic $X(5568)$ state by D0
Collaboration, we study the four-quark system $us\bar{b}\bar{d}$ with quantum
numbers $J^P=0^+$ in the framework of chiral quark model. Two structures,
diquark-antidiquark and meson-meson, with all possible color configurations are
investigated by using Gaussian expansion method. The results show that energies
of the tetraquark states with diquark-antiquark structure are too high to the
candidate of $X(5568)$, and no molecular structure can be formed in our
calculations. The calculation is also extended to the four-quark system
$us\bar{c}\bar{d}$ and the same results as that of $us\bar{b}\bar{d}$ are
obtained.

23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an