Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the production cross section of prompt J/psi mesons in
  association with a W boson in pp collisions at sqrt{s}=7 TeV with the ATLAS
  detector   The process pp--> W + J/psi provides a powerful probe of the production
mechanism of charmonium in hadronic collisions, and is also sensitive to
multiple parton interactions in the colliding protons. Using the 2011 ATLAS
dataset of 4.5 fb-1 of sqrt{s} = 7 TeV pp collisions at the LHC, the first
observation is made of the production of W + prompt J/psi events in hadronic
collisions, using W-->mu+nu and J/psi-->mu+mu. A yield of 27.4+7.5-6.5 W +
prompt J/psi events is observed, with a statistical significance of 5.1 sigma.
The production rate as a ratio to the inclusive W boson production rate is
measured, and the double parton scattering contribution to the cross section is
estimated.

36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph