Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure of scalar mesons and the Higgs sector of strong interaction   The scalar mesons $\sigma(600)$, $\kappa(800)$, $f_0(980)$ and $a_0(980)$
together with the pseudo Goldstone bosons $\pi$, $K$, and $\eta$ may be
considered as the Higgs sector of strong interaction. After a long time of
uncertainty about the internal structure of the scalar mesons there now seems
to be consistency which is in line with the major parts of experimental
observations. Great progress has been made by introducing the unified model of
Close and T\"ornqvist. This model states that mesons below 1 GeV may be
understood as $q^2\bar{q}^2$ in S-wave with some $q\bar{q}$ in P-wave in the
center, further out they rearrange as $(q\bar{q})^2$ and finally as meson-meson
states. The P-wave component inherent in the structure of the neutral scalar
mesons can be understood as a doorway state for the formation of the scalar
meson via two-photon fusion, whereas in nucleon Compton scattering these P-wave
components serve as intermediate states. The masses of the scalar mesons are
predicted in terms of spontaneous and explicit symmetry breaking.

10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
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The categories of this paper are: eess
22
The categories of this paper are: chao-dyn