Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Search for Point Sources of EeV Neutrons   A thorough search of the sky exposed at the Pierre Auger Cosmic Ray
Observatory reveals no statistically significant excess of events in any small
solid angle that would be indicative of a flux of neutral particles from a
discrete source. The search covers from -90 to +15 degrees in declination using
four different energy ranges above 1 EeV (10^18 eV). The method used in this
search is more sensitive to neutrons than to photons. The upper limit on a
neutron flux is derived for a dense grid of directions for each of the four
energy ranges. These results constrain scenarios for the production of
ultra-high energy cosmic rays in the Galaxy.

31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio