Unitarity bounds of astrophysical neutrinos
The flavor composition of astrophysical neutrinos observed at neutrino telescopes is related to the initial composition at their sources via oscillation-averaged flavor transitions. If the time evolution of the neutrino flavor states is unitary, the probability of neutrinos changing flavor is solely determined by the unitary mixing matrix that relates the neutrino flavor and propagation eigenstates. In this paper we derive general bounds on the flavor composition of TeV–PeV astrophysical neutrinos based on unitarity constraints. These bounds are useful for studying the flavor composition of high-energy neutrinos, where energy-dependent nonstandard flavor mixing can dominate over the standard mixing observed in accelerator, reactor, and atmospheric neutrino oscillations.
© 2018 American Physical Society. (Received 8 October 2018; published 28 December 2018) We would like to thank Guoyuan Huang for useful comments on our manuscript. M. A. and M. B. acknowledge support from Danmarks Grundforskningsfond (Project No. 1041811001) and Villum Fonden (Projects No. 18994 and No. 13164, respectively). S. M. would like to thank Thomas Greve and the Caltech SURF program for financial support.
Accepted Version - 1810.00893.pdf
Published - PhysRevD.98.123023.pdf