Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The neutron-proton charge-exchange amplitudes measured in the dp -> ppn
  reaction   The unpolarised differential cross section and the two deuteron tensor
analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange
reaction have been measured with the ANKE spectrometer at the COSY storage
ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were
obtained for small momentum transfers to a (pp) system with low excitation
energy. The results at the three lower energies are consistent with impulse
approximation predictions based upon the current knowledge of the
neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far
more uncertain, agreement requires a reduction in the overall double-spin-flip
contribution, with an especially significant effect in the longitudinal
direction. These conclusions are supported by measurements of the
deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were
carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The
values obtained for the proton analysing power also suggest the need for a
radical re-evaluation of the neutron-proton elastic scattering amplitudes at
the higher energy. It is therefore clear that such measurements can provide a
valuable addition to the neutron-proton database in the charge-exchange region.

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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: gr-qc
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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: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con