Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observational Constraints on the Ultra-high Energy Cosmic Neutrino Flux
  from the Second Flight of the ANITA Experiment   The Antarctic Impulsive Transient Antenna (ANITA) completed its second
long-duration balloon flight in January 2009, with 31 days aloft (28.5 live
days) over Antarctica. ANITA searches for impulsive coherent radio Cherenkov
emission from 200 to 1200 MHz, arising from the Askaryan charge excess in
ultra-high energy neutrino-induced cascades within Antarctic ice. This flight
included significant improvements over the first flight in the payload
sensitivity, efficiency, and a flight trajectory over deeper ice. Analysis of
in-flight calibration pulses from surface and sub-surface locations verifies
the expected sensitivity. In a blind analysis, we find 2 surviving events on a
background, mostly anthropogenic, of 0.97+-0.42 events. We set the strongest
limit to date for 1-1000 EeV cosmic neutrinos, excluding several current
cosmogenic neutrino models.

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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ