Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analysis of a Tau Neutrino Origin for the Near-Horizon Air Shower Events
  Observed by the Fourth Flight of the Antarctic Impulsive Transient Antenna
  (ANITA)   We study in detail the sensitivity of the Antarctic Impulsive Transient
Antenna (ANITA) to possible $\nu_\tau$ point source fluxes detected via
$\tau$-lepton-induced air showers. This investigation is framed around the
observation of four upward-going extensive air shower events very close to the
horizon seen in ANITA-IV. We find that these four upgoing events are not
observationally inconsistent with $\tau$-induced EASs from Earth-skimming
$\nu_\tau$, both in their spectral properties as well as in their observed
locations on the sky. These four events, as well as the overall diffuse and
point source exposure to Earth-skimming $\nu_\tau$, are also compared against
published ultrahigh-energy neutrino limits from the Pierre Auger Observatory.
While none of these four events occurred at sky locations simultaneously
visible by Auger, the implied fluence necessary for ANITA to observe these
events is in strong tension with limits set by Auger across a wide range of
energies and is additionally in tension with ANITA's Askaryan in-ice neutrino
channel above $10^{19}$ eV. We conclude by discussing some of the technical
challenges with simulating and analyzing these near horizon events and the
potential for future observatories to observe similar events.

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The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics