Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Production of vector mesons and measurement of the hadronic component of
  photon light-cone wave function at HERA   A detailed study of vector meson production ($\phi$ and $J/\psi$) in $e^\pm
p$ collisions at HERA with the ZEUS and H1 detector has been performed. The
cross sections are measured as a function of $Q^2$, $W$ and $t$. In this
contribution, the results are summarised, compared to theoretical calculations
and the dynamical picture emerging in perturbative QCD is highlighted. The
measurement of the hadronic component of the photon light-cone wave function in
the exclusive production of di-pions, $ep\to e \pi^+\pi^- p$ is also reported.

32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con