Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of Cosmic Rays from ground: an Introduction   Cosmic rays are the most outstanding example of accelerated particles. They
are about 1\% of the total mass of the Universe, so that cosmic rays would
represent by far the most important energy transformation process of the
Universe. Despite large progresses in building new detectors and in the
analysis techniques, the key questions concerning origin, acceleration and
propagation of the radiation are still open. One of the reasons is that there
are significant discrepancies among the different results obtained by
experiments located at ground probably due to unknown systematic errors
affecting the measurements.
  In this note we will focus on detection of Galactic CRs from ground with EAS
arrays. This is not a place for a complete review of CR physics (for which we
recommend, for instance
\cite{spurio,gaisser,grieder,longair,kampert,blasi,kachelriess}) but only to
provide elements useful to understand the basic techniques used in
reconstructing primary particle characteristics (energy, mass and arrival
direction) from ground, and to show why indirect measurements are difficult and
results still conflicting.

27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org