Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $J/\psi$ polarization in p+p collisions at $\sqrt{s}$ = 200 GeV in STAR   We report on a polarization measurement of inclusive $J/\psi$ mesons in the
di-electron decay channel at mid-rapidity at 2 $<p_{T}<$ 6 GeV/$c$ in $p+p$
collisions at $\sqrt{s}$ = 200 GeV. Data were taken with the STAR detector at
RHIC. The $J/\psi$ polarization measurement should help to distinguish between
different models of the $J/\psi$ production mechanism since they predict
different $p_{T}$ dependences of the $J/\psi$ polarization. In this analysis,
$J/\psi$ polarization is studied in the helicity frame. The polarization
parameter $\lambda_{\theta}$ measured at RHIC becomes smaller towards high
$p_{T}$, indicating more longitudinal $J/\psi$ polarization as $p_{T}$
increases. The result is compared with predictions of presently available
models.

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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: astro-ph
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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: math-ph
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
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The categories of this paper are: econ
32
The categories of this paper are: atom-ph