Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effects of the direct light in the surface detectors (SD) of the Pierre
  Auger Observatory and their change in time   Cosmic Rays (CR) are particles which come to the earth from Universe. Their
origin and production mechanisms are still unknown. The Pierre Auger
Observatory is located in Mendoza, Argentina. It is dedicated to the study of
CR. When CR arrive to the earth's atmosphere they produce a shower of secondary
particles called \textit{air shower}. The surface detector (SD) of the Pierre
Auger Observatory consists of tanks full of pure water, where CR produce
\textit{Cherenkov radiation}, when going through them. This light is detected
by three photomultiplier tubes (PMT) located on the top of each tank. Depending
of the angle of arrival direction of the primary CR, each PMT is able to
register different signal than the other. The goal of this study is to look at
these effects of direct light on the PMT's to explore if they change in time.
The obtained results may give information about the physical status of the
tanks in order to monitor the work of the SD, and to estimate possible
systematic effects on the measurements. The current results of this study are
shown.

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The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
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The categories of this paper are: econ
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin