Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A phenomenological negatively charged pion-proton scattering length from
  pionic hydrogen   We derive a closed, model independent, expression for the electromagnetic
correction factor to a phenomenological hadronic scattering length extracted
from a hydrogenic atom. It is obtained in a non-relativistic approach and in
the limit of a short ranged hadronic interaction to terms of order
((alpha)**2)(log(alpha)) using an extended charge distribution. A hadronic
negatively charged pion-proton scattering length of 0.0870(5), in units of
inverse charged pion-mass, is deduced, leading to a pion-nucleon coupling
constant from the GMO relation equals to 14.04(17).

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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-lat