Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HERA Collider Physics   HERA, the first electron-proton collider, has been delivering luminosity
since 1992. It is the natural extension of an impressive series of fixed-target
lepton-nucleon scattering experiments. The increase of a factor ten in
center-of-mass energy over that available for fixed-target experiments has
allowed the discovery of several important results, such as the large number of
slow partons in the proton, and the sizeable diffractive cross section at large
$Q^2$. Recent data point to a possible deviation from Standard Model
expectations at very high $Q^2$, highlighting the physics potential of HERA for
new effects. The HERA program is currently in a transition period. The first
six years of data taking have primarily elucidated the structure of the proton,
allowed detailed QCD studies and had a strong impact on the understanding of
QCD dynamics. The coming years will bring the era of electroweak studies and
high $Q^2$ measurements. This is therefore an appropriate juncture at which to
review HERA results.

27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph