Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for production of single top quarks   We present first evidence for the production of single top quarks in the D0
detector at the Fermilab Tevatron ppbar collider. The standard model predicts
that the electroweak interaction can produce a top quark together with an
antibottom quark or light quark, without the antiparticle top quark partner
that is always produced from strong coupling processes. Top quarks were first
observed in pair production in 1995, and since then, single top quark
production has been searched for in ever larger datasets. In this analysis, we
select events from a 0.9 fb-1 dataset that have an electron or muon and missing
transverse energy from the decay of a W boson from the top quark decay, and
two, three, or four jets, with one or two of the jets identified as originating
from a b hadron decay. The selected events are mostly backgrounds such as
W+jets and ttbar events, which we separate from the expected signals using
three multivariate analysis techniques: boosted decision trees, Bayesian neural
networks, and matrix element calculations. A binned likelihood fit of the
signal cross section plus background to the data from the combination of the
results from the three analysis methods gives a cross section for single top
quark production of 4.7 +- 1.3 pb. The probability to measure a cross section
at this value or higher in the absence of signal is 0.014%, corresponding to a
3.6 standard deviation significance. The measured cross section value is
compatible at the 10% level with the standard model prediction for electroweak
top quark production.

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The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
2
The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph