Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Helicity fractions of W bosons from top quark decays at NNLO in QCD   Decay rates of unpolarized top quarks into longitudinally and transversally
polarized W bosons are calculated to second order in the strong coupling
constant alpha_s. Including the finite bottom quark mass and electroweak
effects, the Standard Model predictions for the W boson helicity fractions are
F_L=0.687(5), F_+=0.0017(1), and F_-=0.311(5).

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The categories of this paper are: astro-ph
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: chao-dyn