Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-loop QED Operator Matrix Elements with Massive External Fermion
  Lines   The two-loop massive operator matrix elements for the fermionic local
twist--2 operators with external massive fermion lines in Quantum
Electrodynamics (QED) are calculated up to the constant terms in the
dimensional parameter $\epsilon = D - 4$. We investigate the hypothesis of Ref.
\cite{BBN} that the 2--loop QED initial state corrections to $e^+e^-$
annihilation into a virtual neutral gauge boson, except power corrections of
$O((m_f^2/s)^k), k \geq 1$, can be represented in terms of these matrix
elements and the massless 2-loop Wilson coefficients of the Drell-Yan process.

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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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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: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: astro-ph
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol