We show that the PeV neutrinos detected by IceCube put unique constraints on "secret" interactions of neutrinos with the cosmic neutrino background (CνB). The coupling must be g < 0.03 for the mediating boson mass mX ≲ 2MeV, g/mX < 5 GeV-1 for mX ≳ 20MeV, and g/mX < 0.07 GeV-1 in between. We also investigate the possibility that neutrino cascades degrade highenergy neutrinos to PeV energies by upgrading CνB where the energy flux of PeV neutrinos can coincide with the Waxman-Bahcall bound or the cosmogenic neutrino flux for protons, thanks to energy conservation. However, a large coupling is required, which is disfavored by laboratory decay constraints. The suppression of PeV-EeV neutrinos is a testable prediction for the Askaryan Radio Array.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)