Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recent results from NA48/2 and NA62 experiments at CERN   The NA48/2 and $\text{NA62}\text{-}{\text{R}_\text{K}}$ experiments at the
CERN SPS collected a large sample of charged kaon decays in flight.
$\text{NA62}\text{-}{\text{R}_\text{K}}$ was running in 2007-08 with a highly
efficient minimum bias trigger for decays into electrons. A preliminary
measurement of the electromagnetic transition form factor slope of the $\pi^0$
from $1.05\times 10^{6}$ fully reconstructed $\pi^0$ Dalitz decays is
presented. The obtained value $a = (3.70 \pm 0.53_\text{stat} \pm
0.36_\text{syst})\times 10^{-2}$ represents a $5.8\sigma$ observation of a
non-zero slope in the time-like region of momentum transfer. An upper limit on
the rate of a lepton number violating decay $K^\pm\to\pi^\mp\mu^\pm\mu^\pm$ is
reported from $\sim 1.6\times 10^{11} K^\pm$ decays at NA48/2 in 2003-04:
$\mathcal{B} < 8.6\times 10^{-11}$ at $90 \%$ CL. Searches for heavy sterile
neutrino $N_4$ and inflaton $\chi$ resonances in $K^\pm\to\pi\mu\mu$ decays are
reported. No signal is observed and upper limits on the products
$\mathcal{B}(K^\pm\to\mu^\pm N_4)\mathcal{B}(N_4\to\pi^\mp\mu^\pm)$ and
$\mathcal{B}(K^\pm\to\pi^\pm \chi)\mathcal{B}(\chi\to\mu^+\mu^-)$ are set in
the range $10^{-10}-10^{-9}$ for resonance lifetimes up to $100~\text{ps}$. The
result of a search for dark photon with the same sample of decays is also
reported. In the absence of observed signal, the limits on the mixing parameter
$\varepsilon^2$ in the range $9-70~\text{MeV/c}^{2}$ are improved.

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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex
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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: cmp-lg
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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga