Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Intrinsic Charm Contribution to Double Quarkonium Hadroproduction   Double $J/\psi$ production has been observed by the NA3 collaboration in $\pi
N$ and $p N$ collisions with a cross section of the order of 20-30 pb. The
$\psi \psi$ pairs measured in $\pi^- $ nucleus interactions at 150 and 280
GeV$/c$ are observed to carry an anomalously large fraction of the projectile
momentum in the laboratory frame, $x_{\psi \psi} \geq 0.6$ at 150 GeV$/c$ and
$\geq 0.4$ at 280 GeV$/c$. We postulate that these forward $\psi \psi$ pairs
are created by the materialization of Fock states in the projectile containing
two pairs of intrinsic $c \overline c$ quarks. We calculate the overlap of the
charmonium states with the $|\overline u d c \overline c c \overline c \rangle$
Fock state as described by the intrinsic charm model and find that the $\pi^- N
\rightarrow \psi \psi$ longitudinal momentum and invariant mass distributions
are both well reproduced. We also discuss double $J/\psi$ production in $pN$
interactions and the implications for other heavy quarkonium production
channels in QCD.

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The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org