Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is
  the Universe?   The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a
low-energy threshold, has detected very-high-energy gamma rays from a giant
flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C
279, at a distance of more than 5 billion light-years (a redshift of 0.536). No
quasar has been observed previously in very-high-energy gamma radiation, and
this is also the most distant object detected emitting gamma rays above 50
gigaelectron volts. Since high-energy gamma rays may be stopped by interacting
with the diffuse background light in the universe, the observations by MAGIC
imply a low amount for such light, consistent with that known from galaxy
counts.

8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an