Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Results from the IceTop Air Shower Array   IceTop is a 1 km^2 air shower detector presently under construction as a part
of the IceCube Observatory at South Pole. It will consist of 80 detector
stations, each equipped with two ice Cherenkov tanks, which cover 1 km^2. In
2008, the detector is half completed. One of the design goals of the detector
is to investigate cosmic rays in the energy range from the knee up to
approaching 1 EeV and study the mass composition of primary cosmic rays.
  In this report the performance of IceTop, the shower reconstruction
algorithms and first results, obtained with one month of data with an array of
26 stations operated in 2007, will be presented. Preliminary results are shown
for the cosmic ray energy spectrum in the range of 1 to 80 PeV. Being located
at an atmospheric depth of only 700 g/cm^2 at the South Pole, a high
sensitivity of the zenith angle distribution to the mass composition is
observed.
  The main advantage of IceTop, compared to other detectors in this energy
range, is the possibility to measure highly energetic muons from air showers in
coincidence with the IceCube detector. The muon rate at a given air shower
energy is sensitive to mass composition. The prospects of this method and
alternative methods to scrutinise different composition models will be
presented.

9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
3
The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol