Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Twist-4 contributions to the azimuthal asymmetry in SIDIS   We calculate the differential cross section for the unpolarized
semi-inclusive deeply inelastic scattering (SIDIS) process $e^-+N \to e^-+q+X$
in leading order (LO) of perturbative QCD and up to twist-4 in power
corrections and study in particular the azimuthal asymmetry $<cos2\phi>$. The
final results are expressed in terms of transverse momentum dependent (TMD)
parton matrix elements of the target nucleon up to twist-4. %Under the maximal
two-gluon correlation approximation, these TMD parton matrix elements in a
nucleus %can be expressed terms of a Gaussian convolution of that in a nucleon
with the width given by the jet transport %parameter inside cold nuclei. We
also apply it to $e^-+A \to e^-+q+X$ and illustrate numerically the nuclear
dependence of the azimuthal asymmetry $<cos2\phi>$ by using a Gaussian ansatz
for the TMD parton matrix elements.

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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph