Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Open string QED meson description of the X17 particle and dark matter   As a quark and an antiquark cannot be isolated, the intrinsic motion of a
composite $q \bar q$ system in its lowest-energy states lies predominantly in
1+1 dimensions, as in an open string with the quark and the antiquark at its
two ends. Accordingly, we study the lowest-energy states of an open string
$q\bar q$ system in QCD and QED in 1+1 dimensions. We show that $\pi^0, \eta$,
and $\eta'$ can be adequately described as open string $q\bar q$ QCD mesons. By
extrapolating into the $q\bar q$ QED sector in which a quark and an antiquark
interact with the QED interaction, we find an open string isoscalar
$I(J^\pi)$=$0(0^-)$ QED meson state at 17.9$\pm$1.5 MeV and an isovector
$(I(J^\pi)$=$1(0^-), I_3$=0) QED meson state at 36.4$\pm$3.8 MeV. The predicted
masses of the isoscalar and isovector QED mesons are close to the masses of the
hypothetical X17 and E38 particles observed recently, making them good
candidates for these particles. The decay products of QED mesons may show up as
excess $e^+e^-$ and $\gamma \gamma$ pairs in the anomalous soft photon
phenomenon associated with hadron productions in high-energy hadron-proton
collisions and $e^+$-$e^-$ annihilations. Measurements of the invariant masses
of excess $e^+e^-$ and $\gamma \gamma$ pairs will provide tests for the
existence of the open string $q\bar q$ QED mesons. An assembly of gravitating
QED mesons are expected to emit electron-positron pairs and/or gamma rays and
their decay energies and lifetimes will be modified by their gravitational
binding energies. Consequently, a self-gravitating isoscalar QED meson assembly
whose mass $M$ and radius $R$ satisfy $(M/M_\odot)/(R/R_\odot) \gtrsim 4.71
\times 10^5$ will not produce electron-positron pairs nor gamma rays and may be
a good candidate for the primordial dark matter.

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The categories of this paper are: econ
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
2
The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: stat