Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Measurement of ZZ Production in ppbar Collisions at sqrt(s)=1.96
  TeV   We report the first measurement of the cross section for Z boson pair
production at a hadron collider. This result is based on a data sample
corresponding to 1.9 fb-1 of integrated luminosity from ppbar collisions at
sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron.
In the llll channel, we observe three ZZ candidates with an expected background
of 0.096^{+0.092}_{-0.063} events. In the llnunu channel, we use a
leading-order calculation of the relative ZZ and WW event probabilities to
discriminate between signal and background. In the combination of llll and
llnunu channels, we observe an excess of events with a probability of
$5.1\times 10^{-6}$ to be due to the expected background. This corresponds to a
significance of 4.4 standard deviations. The measured cross section is
sigma(ppbar -> ZZ) = 1.4^{+0.7}_{-0.6} (stat.+syst.) pb, consistent with the
standard model expectation.

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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: dg-ga