Lorentz-Invariance Violation with neutrinos from gamma-ray bursts using IceCube High-Energy Starting Events 12-year dataset

Abstract

High-energy astrophysical neutrinos provide a unique probe of Lorentz-invariance violation (LIV), as small energy-dependent deviations from the speed of light can produce measurable time delays over cosmological distances. We search for LIV-induced correlations between neutrinos and gamma-ray bursts using the public 12-year IceCube High-Energy Starting Event dataset and a catalog of 746 bursts with measured redshifts. We develop a likelihood analysis accounting for neutrino directional and energy uncertainties, a possible intrinsic time offset between neutrino and gamma-ray emission, and the decay of superluminal neutrinos expected within effective field theory. For linear LIV, the data show a mild preference over the background-only hypothesis, with a $p$-value of $3.1\%$, corresponding to a one-sided Gaussian significance of approximately $1.9\sigma$. The best fit corresponds to a LIV scale $\Lambda_{\rm LIV}=5.8\times10^{17}\,\mathrm{GeV}$ and is effectively driven by the subluminal component, as superluminal neutrinos are strongly suppressed by LIV-induced decays at the analyzed energies. The preferred LIV scale and the most significant neutrino--gamma-ray burst associations are consistent with previous studies based on different statistical approaches. No evidence for quadratic LIV is found. These results motivate further searches with complementary neutrino datasets, particularly at lower energies, where the superluminal component may become observable.