Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Effect of Doppler Broadening on the $6.3 \ PeV$ $W^-$ Resonance in
  $\bar{\nu}_e e^-$ Collisions   We calculate the Doppler broadening of the $W^-$ resonance produced in
$\bar{\nu}_e e^-$ collisions of cosmic anti-neutrinos with $E_{\nu}\approx 6.3
\ PeV$ with electrons in atoms up to Iron. Revisiting this issue is prompted by
recent observations of PeV neutrinos by Ice-Cube. Despite its poor energy
resolution, the $20\%$ Doppler broadening of the resonance due to electronic
motions can produce observable effects via non-linear neutrino absorption near
the resonance. The attendant suppression of the peak cross section allows
$\bar{\nu}_e$ to travel correspondingly longer distances. While this effect is
unlikely to be directly detected in the near future, it may facilitate
terrestrial tomography at depths of $\sim 10 \ km$, complementing deeper
explorations using the more frequent nuclear interactions at lower energies.

37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
2
The categories of this paper are: math