Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A search for the radiative neutrinoless double electron capture of
  $^{58}$Ni   A search for the radiative neutrinoless double electron capture with single
\gray\ emission has been performed in $^{58}$Ni. Gamma radiation from a 7286 g
nickel sample in natural isotope composition was measured for 58.3 d with an
ultra low background HPGe detector in the Felsenkeller underground laboratory
in Dresden, Germany. A new lower half-life limit of $2.1 \times 10^{21}$ yr
(90% CL) was obtained for this decay mode. This half-life limit is two orders
of magnitude higher than the existing limit for $^{58}$Ni and among the best
half-life limits for neutrinoless double electron capture decays.

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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph