Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Implications of a PeV neutrino spectral cutoff in GRB models   The recent discovery of extragalactic PeV neutrinos opens a new window to the
exploration of cosmic-ray accelerators. The observed PeV neutrino flux is close
to the Waxman-Bahcall upper bound implying that gamma-ray bursts (GRBs) may be
the source of ultra-high energy cosmic rays (UHECRs). Starting with the
assumption of the GRB-UHECR connection, we show using both analytical estimates
and numerical simulations that the observed neutrinos can originate at the jet
as a result of photopion interactions with the following implications: the
neutrino spectra are predicted to have a cutoff at energy $\le 10$ PeV; the
dissipation responsible for the GRB emission and cosmic-ray acceleration takes
place at distances $r_{\rm diss} \approx 3 \times 10^{11}-3 \times 10^{13} \
{\rm cm}$ from the central engine; the Thomson optical depth at the dissipation
region is $\tau_{\rm T} \sim 1$; the jet carries a substantial fraction of its
energy in the form of Poynting flux at the dissipation region, and has a
Lorentz factor $\Gamma \simeq 100-500$. The non-detection of $\sim$PeV
neutrinos coincident with GRBs will indicate that GRBs are either poor cosmic
accelerators or the dissipation takes place at small optical depths in the jet.

34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg