Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Production of Eta Mesons in Proton-Proton Collisions Close to Threshold   A brief experimental overview on the close-to-threshold eta meson production
in proton-proton interactions is presented and the available observables in
measurements with unpolarized and polarized beam and target are discussed.

11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin