We discuss the prospects for next generation neutrino telescopes, such as IceCube, to measure the flavor ratios of high-energy astrophysical neutrinos. The expected flavor ratios at the sources are $$\phi_{\nu_e}:\phi_{\nu_{\mu}}:\phi_{\nu_{\tau}} = 1:2:0$$, and neutrino oscillations quickly transform these to $1:1:1$. The flavor ratios can be deduced from the relative rates of showers ($$\nu_e$$ charged-current, most $$\nu_\tau$$ charged-current, and all flavors neutral-current), muon tracks ($$\nu_\mu$$ charged-current only), and tau lepton lollipops and double-bangs ($$\nu_\tau$$ charged-current only). The peak sensitivities for these interactions are at different neutrino energies, but the flavor ratios can be reliably connected by a reasonable measurement of the spectrum shape. Measurement of the astrophysical neutrino flavor ratios tests the assumed production mechanism and also provides a very long baseline test of a number of exotic scenarios, including neutrino decay, CPT violation, and small-$$\delta m^2$$ oscillations to sterile neutrinos.
Beacom, John F., Bell, Nicole F., Hooper, Dan, Pakvasa, Sandip, & Weiler, Thomas J. (2003). Measuring flavor ratios of high-energy astrophysical neutrinos. Phys.Rev.D, 68. https://doi.org/10.1103/PhysRevD.68.093005
@article{osti_1875890,
author = {Beacom, John F. and Bell, Nicole F. and Hooper, Dan and Pakvasa, Sandip and Weiler, Thomas J.},
title = {Measuring flavor ratios of high-energy astrophysical neutrinos},
annote = {We discuss the prospects for next generation neutrino telescopes, such as IceCube, to measure the flavor ratios of high-energy astrophysical neutrinos. The expected flavor ratios at the sources are $\phi_{\nu_e}:\phi_{\nu_{\mu}}:\phi_{\nu_{\tau}} = 1:2:0$, and neutrino oscillations quickly transform these to $1:1:1$. The flavor ratios can be deduced from the relative rates of showers ($\nu_e$ charged-current, most $\nu_\tau$ charged-current, and all flavors neutral-current), muon tracks ($\nu_\mu$ charged-current only), and tau lepton lollipops and double-bangs ($\nu_\tau$ charged-current only). The peak sensitivities for these interactions are at different neutrino energies, but the flavor ratios can be reliably connected by a reasonable measurement of the spectrum shape. Measurement of the astrophysical neutrino flavor ratios tests the assumed production mechanism and also provides a very long baseline test of a number of exotic scenarios, including neutrino decay, CPT violation, and small-$\delta m^2$ oscillations to sterile neutrinos.},
doi = {10.1103/PhysRevD.68.093005},
url = {https://www.osti.gov/biblio/1875890},
journal = {Phys.Rev.D},
volume = {68},
place = {United States},
year = {2003},
month = {07}}
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