Stringent constraint on neutrino Lorentz-invariance violation from the two IceCube PeV neutrinos

TL;DR

This paper uses two PeV neutrino events detected by IceCube to set the strongest constraints on neutrino Lorentz-invariance violation, limiting superluminal effects and constraining quantum gravity models.

Contribution

It provides the most stringent bounds on neutrino LIV using astrophysical neutrino observations, especially from IceCube's PeV events.

Findings

LIV parameter delta < 10^(-18) for superluminal neutrinos

Constraints imply quantum gravity scale M_QG >~ 10^5 M_Pl

Limits are the strongest to date from astrophysical neutrino data

Abstract

It has been speculated that Lorentz-invariance violation (LIV) might be generated by quantum-gravity (QG) effects. As a consequence, particles may not travel at the universal speed of light. In particular, superluminal extragalactic neutrinos would rapidly lose energy via the bremssthralung of electron-positron pairs (nu -> nu e+ e-), damping their initial energy into electromagnetic cascades, a figure constrained by Fermi-LAT data. We show that the two cascade neutrino events with energies around 1 PeV recently detected by IceCube -if attributed to extragalactic diffuse events, as it appears likely- can place the strongest bound on LIV in the neutrino sector, namely delta =(v^2-1) < O(10^(-18)), corresponding to a QG scale M_QG ~ 10^5 M_Pl (M_QG >~ 10^(-4) M_Pl) for a linear (quadratic) LIV, at least for models inducing superluminal neutrino effects (delta > 0).