Neutrino Pair Cerenkov Radiation for Tachyonic Neutrinos

TL;DR

This paper explores a novel decay process for hypothetical tachyonic neutrinos with space-like dispersion relations, revealing an energy loss mechanism that does not conflict with IceCube PeV neutrino observations.

Contribution

It introduces a new decay process for tachyonic neutrinos, showing the absence of a threshold and its implications for neutrino energy loss models.

Findings

Tachyonic neutrinos can emit neutrino pairs without a threshold.

The decay rate and energy loss are small, avoiding conflict with IceCube data.

Tachyonic models are less constrained by cosmic neutrino observations.

Abstract

The emission of a charged light lepton pair by a superluminal neutrino has been identified as a major factor in the energy loss of highly energetic neutrinos. The observation of PeV neutrinos by IceCube implies their stability against lepton pair Cerenkov radiation. Under the assumption of a Lorentz-violating dispersion relation for highly energetic superluminal neutrinos, one may thus constrain the Lorentz-violating parameters. A kinematically different situation arises when one assumes a Lorentz-covariant, space-like dispersion relation for hypothetical tachyonic neutrinos, as an alternative to Lorentz-violating theories. We here discuss a hitherto neglected decay process, where a highly energetic tachyonic neutrinos may emit other (space-like, tachyonic) neutrino pairs. We find that the space-like dispersion relation implies the absence of a q^2 threshold for the production of a tachyonic neutrino-antineutrino pair, thus leading to the dominant additional energy loss mechanism for an oncoming tachyonic neutrino in the medium-energy domain. Surprisingly, the small absolute value of the decay rate and energy loss rate in the tachyonic model imply that these models, in contrast to the Lorentz-violating theories, are not pressured by the cosmic PeV neutrinos registered by the IceCube collaboration.