Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the Transverse Single Spin Asymmetry of $p$ +
  $p^\uparrow$ $\rightarrow$ $\eta$ + $X$ at $\sqrt{s}$ = 200 GeV   The measurement of transverse single spin asymmetries ($A_N$) provides
insight into the structure of the nucleon. Several mechanisms have been
proposed that attempt to explain $A_N$ based on QCD, and additional
measurements of $A_N$ for different processes further constrain these models.
Using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC), we
study transversely polarized p+p collisions. Results from PHENIX and other
experiments show significant asymmetries in the forward region, which could be
due to contributions from both the Sivers and the Collins effects. Studying the
species as well as the kinematic dependencies of these transverse single spin
asymmetries will help to disentangle the origin of the observed asymmetries.
Therefore, measurements of $A_N$ with inclusive $\eta$ mesons at forward
rapidities are an important tool for the understanding of these asymmetries. In
2008, the PHENIX experiment collected 5.2 pb$^{-1}$ integrated luminosity in
$p^\uparrow+p$ collisions at $\sqrt{s}$ = 200 GeV. The status of the asymmetry
analysis of $\eta$ mesons at forward rapidity will be shown.

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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat