Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the Proton Structure Function ${F_2}$ at low ${x}$ and
  low ${Q^2}$ at HERA   We report on a measurement of the proton structure function $F_2$ in the
range $3.5\times10^{-5}\leq x \leq 4\times10^{-3}$ and 1.5 ${\rm GeV^2} \leq
Q^2 \leq15$ ${\rm GeV^2}$ at the $ep$ collider HERA operating at a
centre-of-mass energy of $\sqrt{s} = 300$ ${\rm GeV}$. The rise of $F_2$ with
decreasing $x$ observed in the previous HERA measurements persists in this
lower $x$ and $Q^2$ range. The $Q^2$ evolution of $F_2$, even at the lowest
$Q^2$ and $x$ measured, is consistent with perturbative QCD.

14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys