[Paper Review] Possible relevance of quantum spacetime for neutrino-telescope data analyses

Giovanni Amelino-Camelia, D. Guetta+1 more|arXiv (Cornell University)|Mar 7, 2013

Noncommutative and Quantum Gravity Theories1 references3 citations

TL;DR

This paper proposes that Lorentz invariance violation (LIV) in quantum spacetime could explain early-arriving high-energy neutrinos detected by IceCube that precede gamma-ray bursts (GRBs), suggesting that some neutrinos previously dismissed as background may instead be GRB-associated. Using a LIV model with a mass scale $ M_{LIV} \lesssim 0.05M_P $, the authors find that up to two of three candidate neutrinos (1.3 TeV, 3.3 TeV, 109 TeV) could be GRB neutrinos, offering a plausible alternative to standard background assumptions.

ABSTRACT

One of the primary goals of neutrino telescopes, such as IceCube, is the discovery of neutrinos emitted by gamma-ray bursts (GRBs). Another source of interest in the results obtained by these telescopes is their possible use for tests of the applicability of Einstein's Special Relativity to neutrinos, particularly with respect to modifications that lead to Lorentz invariance violation that have been conjectured by some models of quantum space-time. We examine here the fascinating scenario in which these two aspects of neutrino-telescope physics require a combined analysis. We discuss how neutrinos that one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. As an illustrative example we examine three IceCube high energy neutrinos that arrived hours before GRBs (but from the same direction) and we find that the available, IceCube data, while inconclusive, is compatible with a scenario in which one or two of these neutrinos were GRB neutrinos and their earlier arrival reflects Lorentz invariance violation. We outline how future analyses of neutrino data should be done in order to systematically test this possibility.

Motivation & Objective

• To re-evaluate IceCube neutrino candidates that arrived before GRBs, challenging the assumption that temporal coincidence is required for GRB association.
• To investigate whether Lorentz invariance violation (LIV) in quantum spacetime could explain early neutrino arrivals, thus reconciling IceCube's non-detection of GRB neutrinos with theoretical predictions.
• To propose a new data analysis framework that incorporates LIV-induced time delays for neutrinos, enabling joint testing of multiple events with a single $ M_{LIV} $ parameter.
• To assess the compatibility of observed neutrino data with GRB emission models under LIV, particularly for high-redshift and short-duration GRBs.
• To motivate future neutrino telescope analyses that adopt a Bayesian prior incorporating LIV time delays, improving sensitivity to quantum spacetime effects.

Proposed method

• Adopt a LIV model where neutrino propagation speed depends on energy and redshift via $ t_{\text{LIV}}(E,z,M_{LIV}) $, with $ M_{LIV} $ as the quantum spacetime scale.
• Use redshift estimates for GRBs (e.g., $ z < 0.35 $ for long GRBs, $ 0.4 < z < 5.5 $ for GRB091230A) to compute expected time delays due to LIV.
• Evaluate the consistency of three IceCube neutrino candidates (1.3 TeV, 3.3 TeV, 109 TeV) with GRB association under LIV, assuming they originated from the same GRB source.
• Apply a Bayesian-like analysis framework, comparing standard uniform-prior models with a new prior that accounts for LIV-induced time shifts in neutrino detection windows.
• Estimate $ M_{LIV} $ values compatible with each event by requiring that the observed time lead is consistent with LIV predictions, using known GRB redshifts and neutrino energies.
• Assess the plausibility of multiple neutrino events being GRB-associated under LIV, considering both background likelihood and model consistency.

Experimental results

Research questions

• RQ1 Can Lorentz invariance violation (LIV) in quantum spacetime explain the early arrival of high-energy neutrinos detected by IceCube that precede gamma-ray bursts (GRBs)?
• RQ2 What values of the LIV scale $ M_{LIV} $ are compatible with the observed time delays of three IceCube neutrino candidates relative to their associated GRBs?
• RQ3 Is it plausible that one or two of the three neutrino candidates (1.3 TeV, 3.3 TeV, 109 TeV) are GRB-associated neutrinos if LIV is present?
• RQ4 How does incorporating LIV into the analysis prior affect the probability of associating neutrinos with GRBs, compared to standard background-only models?
• RQ5 What constraints on $ M_{LIV} $ can be derived from the combined data of multiple neutrino-GRB pairs, especially when considering different GRB types (long vs. short) and redshifts?

Key findings

• The 1.3 TeV neutrino from GRB090417B, arriving 2249 seconds before the GRB trigger, is compatible with being a GRB neutrino if $ M_{LIV} \lesssim 0.01M_P $, assuming a redshift $ z < 0.35 $.
• The 3.3 TeV neutrino from the short GRB090219, arriving 3594 seconds early, is compatible with GRB association for $ M_{LIV} \lesssim 0.05M_P $, consistent with the short burst's likely low redshift.
• The 109 TeV neutrino from GRB091230A, detected 14 hours before the GRB, is compatible with GRB origin for $ 0.02M_P < M_{LIV} < 0.5M_P $, assuming $ 0.4 < z < 5.5 $.
• A consistent interpretation of both the 109 TeV and 3.3 TeV events as GRB neutrinos requires $ 0.02M_P \lesssim M_{LIV} \lesssim 0.05M_P $, suggesting a narrow range of LIV scale values.
• The combined data suggest that at most two of the three neutrino candidates could be GRB-associated under LIV, with the most plausible scenario involving $ M_{LIV} \lesssim 0.05M_P $.
• The results imply that if confirmed, such LIV would favor quantum spacetime models where particle propagation depends on spin or standard model charges, as opposed to universal LIV.