Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for heavy neutral leptons decaying into muon-pion pairs in the
  MicroBooNE detector   We present upper limits on the production of heavy neutral leptons (HNLs)
decaying to $\mu \pi$ pairs using data collected with the MicroBooNE
liquid-argon time projection chamber (TPC) operating at Fermilab. This search
is the first of its kind performed in a liquid-argon TPC. We use data collected
in 2017 and 2018 corresponding to an exposure of $2.0 \times 10^{20}$ protons
on target from the Fermilab Booster Neutrino Beam, which produces mainly muon
neutrinos with an average energy of $\approx 800$ MeV. HNLs with higher mass
are expected to have a longer time-of-flight to the liquid-argon TPC than
Standard Model neutrinos. The data are therefore recorded with a dedicated
trigger configured to detect HNL decays that occur after the neutrino spill
reaches the detector. We set upper limits at the $90\%$ confidence level on the
element $\lvert U_{\mu4}\rvert^2$ of the extended PMNS mixing matrix in the
range $\lvert U_{\mu4}\rvert^2<(6.6$-$0.9)\times 10^{-7}$ for Dirac HNLs and
$\lvert U_{\mu4}\rvert^2<(4.7$-$0.7)\times 10^{-7}$ for Majorana HNLs, assuming
HNL masses between $260$ and $385$ MeV and $\lvert U_{e 4}\rvert^2 = \lvert
U_{\tau 4}\rvert^2 = 0$.

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The categories of this paper are: hep-ph
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The categories of this paper are: eess
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
16
The categories of this paper are: stat
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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: ao-sci
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The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph