Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mixing of eta-eta' Mesons in J/psi Decays into a Vector and a
  Pseudoscalar Meson   The octet-singlet mixing angle $\theta_P$ in the pseudoscalar meson nonet is
deduced from the rich set of accurate data on $J/\psi$ decays into a vector and
a pseudoscalar meson. Corrections due to non-ideal $\omega$-$\phi$ mixing have
been included for the first time and turn out to be crucial to find $\theta_P =
-16.9 \pm 1.7$ degrees, which is appreciably less negative than previous
results coming from similar analyses.

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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph