Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Multi-Component Measurement of the Cosmic Ray Composition Between
  10^{17} eV and 10^{18} eV   The average mass composition of cosmic rays with primary energies between
$10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting
of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array.
Measurements have been made of the change in the depth of shower maximum,
$X_{max}$, and in the change in the muon density at a fixed core location,
$\rho_\mu(600m)$, as a function of energy. The composition has also been
evaluated in terms of the combination of $X_{max}$ and $\rho_\mu(600m)$. The
results show that the composition is changing from a heavy to lighter mix as
the energy increases.

18
The categories of this paper are: econ
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph