Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic form factors of $\Lambda$ hyperon in the vector meson
  dominance model and a possible explanation of the near-threshold enhancement
  of the $e^+e^- \to \Lambda\bar{\Lambda}$ reaction   The near-threshold $e^+e^- \to \Lambda\bar{\Lambda}$ reaction is studied with
the assumption that the production mechanism is due to a near-$\Lambda
\bar{\Lambda}$-threshold bound state. The cross section of $e^+e^- \to
\Lambda\bar{\Lambda}$ reaction is parametrized in terms of the electromagnetic
form factors of $\Lambda$ hyperon, which are obtained with the vector meson
dominance model. It is shown that the contribution to the $e^+e^- \to
\Lambda\bar{\Lambda}$ reaction from a new narrow state with quantum numbers
$J^{PC}=1^{--}$ is dominant for energies very close to threshold. The mass of
this new state is around 2231 MeV, which is very close to the mass threshold of
$\Lambda \bar{\Lambda}$, while its width is just a few MeV. This gives a
possible solution to the problem that all previous calculations seriously
underestimate the near-threshold total cross section of the $e^+e^- \to
\Lambda\bar{\Lambda}$ reaction. We also note that the near-threshold
enhancement can be also reproduced by including these well established vector
resonances $\omega(1420)$, $\omega(1650)$, $\phi(1680)$, or $\phi(2170)$ with a
Flatt${\rm\acute{e}}$ form for their total decay width, and a strong coupling
to the $\Lambda\bar{\Lambda}$ channel.

18
The categories of this paper are: econ
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph