Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single Transverse-Spin Asymmetry in Very Forward and Very Backward
  Neutral Particle Production for Polarized Proton Collisions at sqrt{s} = 200
  GeV   In the 2001-2002 running period of the Relativistic Heavy Ion Collider
(RHIC), transversely polarized protons were accelerated to 100 GeV for the
first time, with collisions at sqrt{s} = 200 GeV. We present results from this
run for single transverse spin asymmetries for inclusive production of neutral
pions, photons and neutrons of the energy region 20 - 100 GeV for forward and
backward production for angles between 0.3 mrad and 2.2 mrad with respect to
the polarized proton direction. An asymmetry of A_N = (-0.090 +- 0.006 +-
0.009) x (1.0^{+0.47}_{-0.24}) was observed for forward neutron production,
where the errors are statistical and systematic, and the scale error is from
the beam polarization uncertainty. The forward photon and pi^0, and backward
neutron, photon, and pi^0 asymmetries were consistent with zero. The large
neutron asymmetry indicates a strong interference between a spin-flip
amplitude, such as one pion exchange which dominates lower energy neutron
production, and remaining spin non-flip amplitudes such as Reggeon exchange.

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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph