wrinkle.uniri.hr

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Summary

Extensive air showers initiated by high-energy gamma rays and cosmic rays provide a unique laboratory for testing Lorentz invariance at energies far beyond those accessible in terrestrial experiments. Lorentz invariance violation (LIV) can modify particle interaction thresholds and cross sections, leading to measurable signatures in shower development, timing, and particle distributions at ground level. Extracting robust constraints therefore requires a coherent framework that combines theory, simulations, detector response, and systematic-uncertainty control.

CALYPSO aims to establish a precision phenomenological and experimental framework for LIV tests using extensive air-shower observations. On the theoretical and computational side, LIV-modifications of particle propagation and interactions will be modelled and implemented in the standard Monte Carlo air-shower simulation tool CORSIKA. Dedicated simulation campaigns will be used to identify observables with enhanced sensitivity to LIV and to quantify the impact of modelling assumptions and experimental systematics.

On the experimental side, the project will design and develop an internal LED calibration unit for the outer-layer detector tanks of SWGO, providing in-situ monitoring of photomultiplier timing offsets and gain during detector operation. Precise in-situ calibration is essential to ensure that instrumental effects do not mimic or obscure LIV signatures, and the developed unit will be prepared for installation at the SWGO pathfinder site.

Finally, the calibrated simulation framework will be applied to existing data from CTAO-LST and MAGIC, using the Crab Nebula as a reference source, to derive quantitative constraints on LIV parameters and to forecast the sensitivity of SWGO.

With its unique combination of theoretical modelling, Monte Carlo simulations, detector calibration, and statistical analysis, CALYPSO will deliver the first end-to-end framework linking LIV theory, shower simulations, detector calibration, and data analysis, enabling robust and competitive tests of fundamental symmetries.

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Objectives

• O1: Fundamental physics with extensive air showers (EAS). Develop a precision phenomenological framework for EAS-based LIV tests: compute LIV-modified electromagnetic interaction cross sections; implement them in CORSIKA 8; identify and characterise sensitive shower observables; set quantitative constraints from existing data obtained with telescopes CTAO-LST and MAGIC; forecast sensitivity for the Southern Wide-field Gamma-ray Observatory (SWGO).
• O2: Experimental calibration and systematics control. Design, develop, and validate an internal LED calibration unit for the outer-layer detector tanks of SWGO, providing in-situ monitoring of photomultiplier timing and gain during detector operation, and prepare the unit for installation at the SWGO pathfinder. This is essential to ensure that detector systematics do not mimic or obscure LIV signatures as investigated under Objective O1.
• O3: Dissemination and outreach. Publish results in leading journals; present at international conferences; communicate findings to the public through outreach events.

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Work plan

The objectives will be reached through six interconnected tasks over a period of 36 months, progressing from theoretical modelling to simulations, calibration, and data analysis.

• T1.1 – LIV-modified interaction calculations (months 1 – 24). Precise calculation of the kinematics and dynamics of particle interactions in the atmosphere, for LIV scenarios in which only photons, or both photons and leptons, are affected. The processes of interest are Bethe–Heitler pair production and bremsstrahlung.
• T1.2 – Implementation in shower simulations (months 7 – 30). Modification of the EAS simulation code CORSIKA 8 with the LIV-modified interactions calculated in T1.1; production of shower simulations with LIV-modified interactions and comparison with the standard shower simulations.
• T1.3 – Data analysis and validation (months 18 – 36). Sensitivity study for SWGO using its expected instrument response functions, and analysis of the Crab Nebula data taken with the MAGIC and CTAO-LST telescopes to understand the influence of LIV-modified showers on the observed spectrum.
• T2.1 – Laboratory setup and prototype design (months 1 – 18). Procurement of equipment and preparation of the laboratory for the development of the internal LED calibration unit; visit to the SWGO detector development group at INFN Napoli and the University of Napoli Federico II; conceptual design of the calibration unit, including LED driver circuit, optical diffuser geometry, and housing.
• T2.2 – Calibration unit development and validation (months 6 – 36). Development, assembly, and validation of the internal LED calibration unit in the Laboratory for Astroparticle Physics at the University of Rijeka; compatibility testing with the INFN Napoli multi-PMT module and preparation for installation at the SWGO pathfinder at Pampa La Bola, Chile.
• T3.1 – Dissemination and outreach (months 1 – 36). Publication of the results in scientific journals, presentations at collaboration meetings and international scientific conferences, and presentation of the research to the general public.

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Team

• Tomislav Terzić (University of Rijeka) – principal investigator; project coordination, procurement of the laboratory equipment, LIV phenomenology, data analysis and statistics
• Filip Reščić (University of Rijeka) – PhD student; LIV interaction calculations, cross-section modelling
• José Manuel Carmona (University of Zaragoza) – senior collaborator; theoretical LIV frameworks, interaction calculations
• Marina Manganaro (University of Rijeka) – laboratory setup, calibration quality control
• Jelena Strišković (Josip Juraj Strossmayer University of Osijek) – calibration system development, photosensor calibration, gamma-ray data analysis
• Mario Pecimotika (Dr. Franjo Tuđman Defense and Security University) – CORSIKA implementation and simulations, gamma-ray data analysis, photosensor calibration
• Postdoctoral researcher (University of Rijeka, to be hired) – laboratory setup, calibration system development, photosensor calibration, systematic uncertainty analysis
• PhD student (University of Rijeka, to be hired) – CORSIKA implementation and simulations, data analysis, calibration tasks

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Partners and infrastructure

The calibration unit prototypes will be designed, built, and tested in the Laboratory for Astroparticle Physics at the University of Rijeka, in close coordination with the INFN Napoli group, where the SWGO multi-PMT readout module is being developed. The LIV-modified interactions will be implemented in CORSIKA 8, in contact with the CORSIKA development team at the Karlsruhe Institute of Technology (KIT). Access to gamma-ray data is ensured through membership in the MAGIC and CTAO-LST collaborations. Shower simulations and data analysis will run on the supercomputer Bura and the advanced computing facility Srce.

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Results and publications

Publications, software, and data releases will be listed here as the project progresses.

News and outreach

Reports on public lectures, media appearances, and other outreach events will be published here.

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CALYPSO is funded by the Croatian Science Foundation under the project number IP-2026-8139.