Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vector meson production at HERA   The rich experimental landscape of exclusive vector meson production at the
high energy electron-proton collider HERA is reviewed, with emphasis on the
transition from soft to hard diffraction and QCD interpretations.

29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc