Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for standard model production of four top quarks in proton-proton
  collisions at sqrt(s) = 13 TeV   A search for events containing four top quarks (ttbar-ttbar) is reported from
proton-proton collisions recorded by the CMS experiment at sqrt(s) = 13 TeV and
corresponding to an integrated luminosity of 2.6 inverse femtobarns. The
analysis considers the single-lepton (e or mu)+jets and the opposite-sign
dilepton (mu+mu-, mu+/- e-/+, or e+e-)+jets channels. It uses boosted decision
trees to combine information on the global event and jet properties to
distinguish between ttbar-ttbar and ttbar production. The number of events
observed after all selection requirements is consistent with expectations from
background and standard model signal predictions, and an upper limit is set on
the cross section for ttbar-ttbar production in the standard model of 94 fb at
95% confidence level (10.2 times the prediction), with an expected limit of 118
fb. This is combined with the results from the published CMS search in the
same-sign dilepton channel, resulting in an improved limit of 69 fb at 95%
confidence level (7.4 times the prediction), with an expected limit of 71 fb.
These are the strongest constraints on the rate of ttbar-ttbar production to
date.

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The categories of this paper are: hep-ph
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The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: physics