Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Collins-Soper Equation for the Energy Evolution of Transverse-Momentum
  and Spin Dependent Parton Distributions   The hadron-energy evolution (Collins and Soper) equation for all the
leading-twist transverse-momentum and spin dependent parton distributions is
derived in the impact parameter space. Based on the result, we present
resummation formulas for the spin structure functions in the semi-inclusive
deep inelastic scattering.

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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: astro-ph
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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex