Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: $e^+e^-$ Pair Production from 10 GeV to 10 ZeV   At very high energies, pair production ($\gamma\to e^+e^-$) exhibits many
interesting features. The momentum transfer from the target is very small, so
the reaction probes the macroscopic properties of the target, rather than
individual nuclei. Interference between interactions with different atoms
reduces the pair production cross section considerably below the Bethe-Heitler
values. At very high energies, photonuclear interactions may outnumber pair
production.
  In contrast, in crystals, the interaction amplitudes may add coherently,
greatly increasing the cross sections. Pair production in matter-free magnetic
fields is also possible. The highest energy pair production occurs at high
energy particle colliders. This article will compare pair production in these
very different regimes.

22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs