Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High Precision Measurements of the Pion Proton Differential Cross
  Section   Study of the elastic scattering can produce a rich information on the
dynamics of the strong interaction. The EPECUR collaboration is aimed at the
research of baryon resonances in the second resonance region via pion-proton
elastic scattering and kaon-lambda production. The experiment features high
statistics and better than 1 MeV resolution in the invariant mass thus allowing
searches for narrow resonances with the coupling to the pi p channel as low as
5%. The experiment is of "formation" type, i.e. the resonances are produced in
s-channel and the scan over the invariant mass is done by the variation of the
incident pion momentum which is measured with the accuracy of 0.1% with a set
of 1 mm pitch proportional chambers located in the first focus of the beam
line. The reaction is identified by a magnetless spectrometer based on wire
drift chambers with a hexagonal structure. Background suppression in this case
depends on the angular resolution, so the amount of matter in the chambers and
the setup was minimized to reduce multiple scattering.
  The measurements started in 2009 with the setup optimized for elastic
pion-proton scattering. With 3 billions of triggers already recorded the
differential cross section of the elastic pi p-scattering on a liquid hydrogen
target in the region of the diffraction minimum is measured with statistical
accuracy about 1% in 1 MeV steps in terms of the invariant mass. The paper
covers the experimental setup, current status and some preliminary results.

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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom