Quantum GRavity seArches with Neutrino Telescopes

Project Information

QGRANT

Grant agreement ID: 101068013

DOI

10.3030/101068013

Project closed

EC signature date 15 June 2022

Start date 1 October 2022

End date 30 September 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 189 687,36

Coordinated by

FRIEDRICH-ALEXANDER-UNIVERSITAET ERLANGEN-NUERNBERG
Germany

Periodic Reporting for period 1 - QGRANT (Quantum GRavity seArches with Neutrino Telescopes)

Reporting period: 2022-10-01 to 2025-09-30

Summary of the context and overall objectives of the project

The QGRANT project operates at the frontier of theoretical and experimental physics, tackling one of the most profound questions in science: the reconciliation of the Standard Model (SM) of particle physics and General Relativity (GR) into a comprehensive theory of Quantum Gravity (QG). Although both SM and GR independently provide extremely accurate descriptions of nature at micro and macro scales, respectively, they are fundamentally incompatible. Their merger is anticipated at the Planck scale, far beyond current experimental reach. Nevertheless, certain predicted effects of QG, such as quantum decoherence (QD) and violations of discrete and space-time symmetries like Lorentz invariance (LI), might be observable at lower energies that are accessible to modern particle physics experiments.
Neutrino telescopes such as IceCube, ANTARES, and KM3NeT offer a unique window into these physics regimes due to their sensitivity across a broad energy range and baseline, functioning as natural interferometers for probing QG-induced effects. Specifically, deviations in neutrino oscillation patterns that could arise from QD or Lorentz invariance violation (LIV) are prime targets for experimental investigation. Exploring these deviations not only constrains QG models but also deepens our understanding of the structure of space-time itself.

Motivation and Pathway to Impact:

The core motivation of QGRANT is to perform the first joint, global analysis for QG signatures in neutrino oscillation data acquired from IceCube, ANTARES, and KM3NeT. The approach includes investigating both QD and LIV effects, aiming to set unprecedented limits on these phenomena, and, incidentally, to probe the fundamental properties of neutrinos such as their Dirac or Majorana nature and potential CPT violation. The project's scientific pathway involves:
1) Enriching the science scope of ANTARES and KM3NeT by performing new QG analyses with 10+ years of data and evaluating the sensitivity of freshly deployed KM3NeT modules.
2) Reinforcing the role of neutrinos as probes for quantum gravity through strong cooperation with theoretical QG experts, particularly those specializing in Loop Quantum Gravity (LQG), and combining the strengths of three global neutrino observatories in a first-of-its-kind analysis.

Political and Strategic Context:

This research aligns with major international scientific priorities in astroparticle physics—pushing the boundaries of fundamental knowledge and experimental techniques. By leveraging the unique environment of the Erlangen Centre for Astroparticle Physics (ECAP), which hosts active groups for all three neutrino telescopes and a close partnership with quantum gravity theory groups, QGRANT maximizes both the scientific and strategic potential of European and global collaborations in this field. The MSCA fellowship provides the necessary international and interdisciplinary framework, fostering long-term human capital development, technology transfer, and global research networks within the European and wider scientific community.

Scale and Significance of Expected Impact

The anticipated impacts are multifaceted and of significant scale:
1) Scientific Impact: Setting new limits on QG phenomena that will influence theoretical model-building and guide future experimental efforts. Results from the joint analysis will be the most sensitive yet, and may lead to the first observation of QG signatures or improved constraints.
2) Strategic Impact: Deepening collaboration among major neutrino observatories and between experimental and theoretical communities, laying the groundwork for next-generation analyses and discoveries.
3) Societal and Outreach Impact: Through open access publishing, outreach programs, and integration of machine learning tools, the project will communicate advances to both scientific and general audiences. The development and release of the Quantum Gravity Neutrino Tool (QGNT) as open-source software will further empower the wider research community.

In summary, QGRANT sets the scene for a transformational advance in both physics and research culture, promising new insights into quantum gravity, neutrino physics, and fundamental symmetries in nature, with broad impact on international science and society.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the funding period, significant progress was made on the scientific goals of QGRANT:


1. Technical Activities

- Joint LIV Search: Led and collaborated on the first ever joint analysis searching for the signatures of Lorentz invariance violation in neutrino oscillations using data from ANTARES, IceCube, and KM3NeT. This work extended the energy and baseline range of previous studies and improved statistical power, providing new sensitivity on isotropic SME coefficients in the neutrino sector.

- Development of Analysis Tools: Developed and released open-source physics tools, including modules for calculations of neutrino oscillations with quantum gravity-induced decoherence and LIV terms. These have been integrated in the official software of major collaborations and shared publicly. See: https://zenodo.org/records/17425187.


2. Main Scientific Outcomes

- Constraints on LIV: Achieved leading constraints on isotropic LIV coefficients across several mass dimensions in the low-energy regime (using KM3NeT/ORCA6 data) and evaluated the sensitivity at higher energies (combining IceCube, ANTARES, and ARCA). The results are the first experimental bounds on certain SME coefficients not previously constrained. This work positions KM3NeT and the combined analysis at the forefront of quantum gravity phenomenology in the neutrino sector.​​

- Quantum Decoherence Studies: Progressed the theoretical and phenomenological investigation of QD effects in neutrino oscillations.

- Relevant Publications: Authored and contributed to high-impact journal articles, notably:

- JCAP 11 (2024) 006: First-principles models of gravitationally induced decoherence in neutrinos.

- JCAP 01 (2025) 063: Discovery potential for QG-induced decoherence in telescopes with dark sector couplings.

- PoS ICRC2023 (2023) 1086: Advanced analysis of LIV in neutrino telescopes.

Multiple major collaborative papers on neutrino oscillations and instrumental developments.


3. Leadership and Contribution to Collaborations:

- Vice-leader of quantum gravity physics groups within European COST actions.

- Supervisor of student theses focused on quantum gravity searches, LIV, and machine learning techniques for event reconstruction and classification.


4. International Recognition and Dissemination

- Invited speaker at key international conferences, schools, and seminars (ICISE, Harvard, DPG, Neutrino Workshop, Nobel Laureate meetings).

- Active participant in scientific and organizational committees for conferences, COST actions, and outreach initiatives.

- Published results in both peer-reviewed journals and open-access repositories (arXiv), and presented latest achievements in talks and poster sessions at leading astroparticle meetings.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Results Beyond the State of the Art:

1) First Global Sensitivity on Lorentz Invariance Violation (LIV) with KM3NeT, ANTARES and IceCube and first upper limits on some LIV parameters with KM3NeT/ORCA6:

- Led the first-ever coordinated search for isotropic LIV effects using combined atmospheric neutrino data from the three largest telescopes: ANTARES, IceCube, KM3NeT.

- Set leading experimental upper limits on both diagonal and off-diagonal SME coefficients for mass dimensions d = 3 up to d=8, and crucially, delivered the first constraints on isotropic diagonal LIV coefficients free from assumptions on astrophysical flavor composition.​

- Achieved competitive upper limits despite limited exposure of KM3NeT/ORCA6, demonstrating the power of synergy between detector platforms.

2) Innovative Methods for LIV and Decoherence Searches:

- Developed state-of-the-art open-source software tools for calculating neutrino oscillations under quantum gravity hypotheses (OscProb::PMNS_LIV, OscProb::PMNS_GQD, OscProb::PMNS_OQS), now adopted within major collaborations and published for community use.​

- Pioneered the application of machine learning, especially graph neural networks, to optimize event reconstruction and classification for next-generation detectors, as recognized in recent collaborative publications.

3) Theoretical Advances:

- Proposed and quantitatively modeled gravitationally-induced decoherence in neutrino oscillations within a microscopic quantum mechanical framework.​


Potential Impacts

1) Scientific Impact:

- Results lay groundwork for future joint multi-experiment analyses, enabling the high-precision testing of quantum gravity models and symmetry violations.

2) Community Uptake and Internationalisation:

- Open-source toolkits and analysis strategies foster adoption across other experiments, broadening reach and accelerating results in multi-messenger neutrino astronomy.

Overview of Results

- New world-leading joint sensitivity (ANTARES, KM3NeT, IceCube) and KM3NeT/ORCA6 constraints on LIV coefficients (d=3–8), with published outcomes referenced in JCAP (2024, 2025), and PoS(ICRC2023), and an internal KM3NeT paper which will be submitted to JHEP in a couple of months.

- Dissemination through international invited talks, leadership roles in strategic collaborations, and implementation of reproducible and open-source analysis tools now available to the global astroparticle physics community.

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