Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of ttbar Spin Correlation in ppbar Collisions Using the CDF
  II Detector at the Tevatron   The ttbar spin correlation at production is a fundamental prediction of QCD
and a potentially incisive test of new physics coupled to top quarks. We
measure the ttbar spin state in ppbar collisions at sqrt(s) = 1.96 TeV using
1001 candidate events in the lepton plus jets decay channel reconstructed in
the CDF II detector. In the helicity basis, for a top-quark mass of 172.5
GeV/c^2, we find a spin correlation coefficient kappa = 0.60 +/- 0.50 (stat)
+/- 0.16 (syst), consistent with the QCD prediction, kappa ~= 0.40.

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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con