Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: LAB observables for the muon polarization in K^+ --> \pi^+ \mu^+ \mu^-   We analyse the muon longitudinal polarization asymmetry \Delta_long in the
decay K^+ --> \pi^+ \mu^+ mu^-. It is stressed that, since the muon helicities
are not Lorentz-invariant quantities, the magnitude of \Delta_long depends in
general on the reference frame. We consider the muon helicities in the LAB
system, and study the sensitivity of the longitudinal polarization asymmetry to
the flavour-mixing parameters in the Standard Model for stopped and in-flight
decaying K^+. A similar analysis is carried out for the decay K_L --> \mu^+
\mu^-. We find that in both cases the asymmetry is diluted when increasing the
energy of the decaying kaons.

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The categories of this paper are: eess
37
The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: stat