Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutrino-photon reactions in astrophysics and cosmology   At energies above the threshold for $W$ production the process $\nu \gamma
\to l W^+$ is competive with $\nu \nu$ scattering at the same center of mass
energies. In a cosmological setting, absorption of ultra high energy neutrinos
by the microwave photon background is comparable to absorption by the neutrino
background. In passing through matter, the process $\nu \to l W^+$ will occur
in the coulomb field of nuclei. For iron, the interaction rate per nucleon is
roughly 20% of the charge current cross-section. The related process,
$\anti\nu_e e^- \to \gamma W^-$ dominates $\anti\nu_e e^-$ scattering for about
a decade in energy above the resonance for $W$ production.

27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th