Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: About virtual pi --> K Meson Oscillations   In the framework of the Standard Model the probability (and time) of pi --> K
transitions (oscillations) are computed. These transitions are virtual ones
since masses of pi and K mesons differ considerably. These transitions
(oscillations) can be registered through K decays after transitions of virtual
K mesons to their own mass shell by using their quasielastic strong
interactions. But for avoiding the background from inelastic K mesons, the
energies E(pi) of pi mesons must be less than the threshold energy of their
creation, i.e. E(pi) < 0.91GeV. The optimal distances for observation of these
oscillations are computed. Solution of the problem of origin of mixing angle in
the theory of vacuum oscillation is given.

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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: stat
1
The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph