Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing small-x parton densities in proton- proton (-nucleus) collisions
  in the very forward direction   We present calculations of several pp scattering cross sections with
potential applications at the LHC. Significantly large rates for momentum
fraction, x, as low as 10^-7 are obtained, allowing for possible extraction of
quark and gluon densities in the proton and nuclei down to these small x values
provided a detector with good acceptance at maximal rapidities is used.

15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin