Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Upper Limits on the Radar Cross Section of Cosmic-Ray Induced
  Extensive Air Showers   TARA (Telescope Array Radar) is a cosmic ray radar detection experiment
colocated with Telescope Array, the conventional surface scintillation detector
(SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA
detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting
antenna which broadcasts the radar carrier over the SD array and within the FD
field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data
since 2013 with the primary goal of observing the radar signatures of extensive
air showers (EAS). Simulations indicate that echoes are expected to be short in
duration (~10 microseconds) and exhibit rapidly changing frequency, with rates
on the order of 1 MHz/microsecond. The EAS radar cross-section (RCS) is
currently unknown although it is the subject of over 70 years of speculation. A
novel signal search technique is described in which the expected radar echo of
a particular air shower is used as a matched filter template and compared to
waveforms obtained by triggering the radar DAQ using the Telescope Array
fluorescence detector. No evidence for the scattering of radio frequency
radiation by EAS is obtained to date. We report the first quantitative RCS
upper limits using EAS that triggered the Telescope Array Fluorescence
Detector.

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The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
3
The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph