1. Search for a diffuse flux of photons with energies above tens of PeV at the Pierre Auger ObservatoryA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, original scientific article Abstract: Diffuse photons of energy above 0.1 PeV, produced through the interactions between cosmic rays and either interstellar matter or background radiation fields, are powerful tracers of the distribution of cosmic rays in the Galaxy. Furthermore, the measurement of a diffuse photon flux would be an important probe to test models of super-heavy dark matter decaying into gamma-rays. In this work, we search for a diffuse photon flux in the energy range between 50 PeV and 200 PeV using data from the Pierre Auger Observatory. For the first time, we combine the air-shower measurements from a 2 sq. km surface array consisting of 19 water-Cherenkov surface detectors, spaced at 433 m, with the muon measurements from an array of buried scintillators placed in the same area. Using 15 months of data, collected while the array was still under construction, we derive upper limits to the integral photon flux ranging from 13.3 to 13.8 per sq. km, per steradian, and per year above tens of PeV. We extend the Pierre Auger Observatory photon search program towards lower energies, covering more than three decades of cosmic-ray energy. This work lays the foundation for future diffuse photon searches: with the data from the next 10 years of operation of the Observatory, this limit is expected to improve by a factor of ∼20.
Keywords: ultra-high-energy (UHE) cosmic rays, UHE photons, Pierre Auger Observatory, diffuse photon flux, extensive air showers, water-Cherenkov surface detectors, underground muon detectors
Published in RUNG: 26.05.2025; Views: 375; Downloads: 6
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2. The Radio Detector of the Pierre Auger ObservatoryJ. R. Hörandel, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, published scientific conference contribution Abstract: To measure the properties of the highest-energy particles in the Universe with unprecedented precision, we have upgraded the Pierre Auger Observatory. A crucial component of this upgrade is the Radio Detector. Radio antennas have been added to all 1660 positions of the surface detector array, covering an area of 3000 sq. km. The antennas detect radio emission, emitted by extensive air showers in the frequency band from 30 to 80 MHz in two polarization directions - one parallel and one perpendicular to the Earth magnetic field. For inclined air showers with zenith angles above 60 degrees, the radio antennas provide a clean measurement of the electromagnetic shower component, while the water-Čerenkov detectors measure the muonic component. Large-scale deployment in the Argentinian Pampa Amarilla started around June 2023 and has been completed in 2024. The deployment is accompanied by extensive calibration efforts both, in the laboratory and in the field. The signal chain is characterized in the laboratory. Galactic radio emission is used as a reference signal and the antenna patterns are verified through in-situ calibrations with a reference antenna. Commissioning of the system is in full progress as well as the analysis of first measured air showers. We present first air showers measured with the largest radio detector for cosmic rays in the world.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, extensive air showers, surface detectors, Water-Cherenkov detectors, Surface Scintillator detectors
Published in RUNG: 16.05.2025; Views: 490; Downloads: 9
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3. Machine learning-based analyses using surface detector data of the Pierre Auger ObservatorySteffen Hahn, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, published scientific conference contribution Abstract: The Pierre Auger Observatory is the largest detector for the study of extensive air showers induced
by ultra-high-energy cosmic rays (UHECRs). Its hybrid detector design allows the simultaneous
observation of different parts of the shower evolution using various detection techniques. To
accurately understand the physics behind the origin of UHECRs, it is essential to determine their
mass composition. However, since UHECRs cannot be measured directly, estimating their masses
is highly non-trivial. The most common approach is to analyze mass-sensitive observables, such as
the number of secondary muons and the atmospheric depth of the shower maximum.
An intriguing part of the shower to estimate these observables is its footprint. The shower footprint is detected by ground-based detectors, such as the Water-Cherenkov detectors (WCDs) of the Surface Detector (SD) of the Observatory, which have an uptime of nearly 100%, resulting in a high number of observed events. However, the spatio-temporal information stored in the shower footprints is highly complex, making it very challenging to analyze the footprints using analytical and phenomenological methods. Therefore, the Pierre Auger Collaboration utilizes machine learning-based algorithms to complement classical methods in order to exploit the measured data with unprecedented precision. In this contribution, we highlight these machine learning-based analyses used to determine high-level shower observables that help to infer the mass of the primary particle, with a particular focus on analyses using the shower footprint detected by the WCDs and the Surface Scintillator Detectors (SSD) of the SD. We show that these novel methods show promising results on simulations and offer improved reconstruction performance when applied to measured data.
Keywords: ultra-high-energy cosmic rays (UHECRs), extensive air showers, Pierre Auger Observatory, surface detector, Water-Cherenkov detectors (WCDs), Surface Scintillator Detectors (SSDs), UHECR mass composition, air-shower footprint, machine learning
Published in RUNG: 16.05.2025; Views: 428; Downloads: 6
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4. The distribution of ultrahigh-energy cosmic rays along the supergalactic plane measured at the Pierre Auger ObservatoryA. Abdul Halim, P. Abreu, M. Aglietta, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, original scientific article Abstract: Ultrahigh-energy cosmic rays are known to be mainly of extragalactic origin, and their propagation is limited by energy losses, so their arrival directions are expected to correlate with the large-scale structure of the local Universe. In this work, we investigate the possible presence of intermediate-scale excesses in the flux of the most energetic cosmic rays from the direction of the supergalactic plane region using events with energies above 20 EeV recorded with the surface detector array of the Pierre Auger Observatory up to 2022 December 31, with a total exposure of 135,000 sq. km sr yr. The strongest indication for an excess that we find, with a posttrial significance of 3.1σ, is in the Centaurus region, as in our previous reports, and it extends down to lower energies than previously studied. We do not find any strong hints of excesses from any other region of the supergalactic plane at the same angular scale. In particular, our results do not confirm the reports by the Telescope Array Collaboration of excesses from two regions in the Northern Hemisphere at the edge of the field of view of the Pierre Auger Observatory. With a comparable integrated exposure over these regions, our results there are in good agreement with the expectations from an isotropic distribution.
Keywords: ultra-high-energy cosmic rays, UHECR propagation, large-scale structure, UHECR energy losses, UHECR deflections, supergalactic plane region, Centaurus region, Pierre Auger Observatory, Auger surface detector array
Published in RUNG: 06.05.2025; Views: 540; Downloads: 5
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5. Isotropy of Cosmic Rays beyond 10[sup]20 eV Favors Their Heavy Mass CompositionR. U. Abbasi, Jon Paul Lundquist, 2024, original scientific article Abstract: We report an estimation of the injected mass composition of ultrahigh energy cosmic rays (UHECRs) at energies higher than 10 EeV. The composition is inferred from an energy-dependent sky distribution of UHECR events observed by the Telescope Array surface detector by comparing it to the Large Scale Structure of the local Universe. In the case of negligible extragalactic magnetic fields (EGMFs), the results are consistent with a relatively heavy injected composition at E ∼ 10 EeV that becomes lighter up to E ∼ 100 EeV, while the composition at E > 100 EeV is very heavy. The latter is true even in the presence of highest experimentally allowed extragalactic magnetic fields, while the composition at lower energies can be light if a strong EGMF is present. The effect of the uncertainty in the galactic magnetic field on these results is subdominant.
Keywords: ultrahigh energy cosmic rays (UHECRs), Large Scale Structure, extragalactic magnetic fields, UHECR propagation, Telescope Array surface detector, UHECR mass composition, UHECR arrival directions
Published in RUNG: 23.04.2025; Views: 445; Downloads: 4
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6. Intermediate fluence downward terrestrial gamma ray flashes as observed by the Telescope Array Surface DetectorR. U. Abbasi, N. Kieu, P. R. Krehbiel, J. W. Belz, M. M. F. Saba, W. Rison, M. A. Stanley, D. Rodeheffer, D. Mazzucco, Jon Paul Lundquist, 2024, original scientific article Abstract: On 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurred during the initial stage of negative cloud‐to‐ground flashes whose return strokes had increasingly large peak currents up to 223 kA, 147 GeV energy deposit in up to 25 1.2 km‐spaced surface detectors, and intermittent bursts of gamma‐rays with total durations up to 717 s. The analyses are based on observations recorded by the TASD network, complemented by data from a 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, and the National Lightning Detection Network. The TGFs of the final two flashes had gamma fluences of and 8, logarithmically bridging the gap between previous TASD and satellite‐based detections. The observations further emphasize the similarity between upward and downward TGF varieties, suggesting a common mechanism for their production.
Keywords: Telescope Array Surface Detector, terrestrial gamma ray flashes, 3D lightning mapping array, broadband VHF interferometer, fast electric field change sensor, high‐speed video camera, National Lightning Detection Network, TGF fluence measurement
Published in RUNG: 23.04.2025; Views: 463; Downloads: 8
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7. First time-resolved leader spectra associated with a downward terrestrial gamma-ray flash detected at the Telescope Array Surface DetectorN. Kieu, R. U. Abbasi, M. M. F. Saba, J. W. Belz, P. R. Krehbiel, M. A. Stanley, F. J. Gordillo-Vazquez, M. Passas-Varo, T. Warner, Jon Paul Lundquist, 2024, original scientific article Abstract: Optical emissions associated with Terrestrial Gamma ray Flashes (TGFs) have recently become important subjects in space‐based and ground‐based observations as they can help us understand how TGFs are produced during thunderstorms. In this paper, we present the first time‐resolved leader spectra of the optical component associated with a downward TGF. The TGF was observed by the Telescope Array Surface Detector (TASD) simultaneously with other lightning detectors, including a Lightning Mapping Array (LMA), an INTerFerometer (INTF), a Fast Antenna (FA), and a spectroscopic system. The spectroscopic system recorded leader spectra at 29,900 frames per second (33.44 s time resolution), covering a spectral range from 400 to 900 nm, with 2.1 nm per pixel. The recordings of the leader spectra began 11.7 ms before the kA return stroke and at a height of 2.37 km above the ground. These spectra reveal that optical emissions of singly ionized nitrogen and oxygen occur between 167 s before and 267 s after the TGF detection, while optical emissions of neutrals (H I, 656 nm; N I, 744 nm, and O I, 777 nm) occur right at the moment of the detection. The time‐dependent spectra reveal differences in the optical emissions of lightning leaders with and without downward TGFs.
Keywords: Telescope Array Surface Detector, terrestrial gamma‐ray flashes, time‐resolved tgf leader spectra
Published in RUNG: 22.04.2025; Views: 474; Downloads: 7
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8. Setup of a surface-mount-technology line : diploma thesisBoban Trajkovski, 2025, undergraduate thesis Abstract: This work aims to describe Surface-Mount Technology (SMT) and the process of setting up the production line. The focus is on a detailed explanation of the SMT line, the machines included in the SMT line, and the necessary steps that must be taken to ensure its optimal performance. The main contribution of this work is a description of the line-setting procedure, where each machine is individually set up with Printed Circuit Board (PCB) parameters adjusted to meet each customer's specific technical requirements. For a clearer explanation, a task flow diagram is provided to show the sequence and functions of the machines in the line. Finally, the conclusion highlights the fully assembled PCB, with all components correctly mounted and functioning. These components are identified and explained individually, along with their specific function and purpose.
Keywords: electronics, surface-mount technology, automated assembly, soldering techniques, component-mounting technologies, surface-mount-technology line optimization
Published in RUNG: 17.04.2025; Views: 737; Downloads: 19
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9. Surface acidity and basicity of ZnAlGaOx catalysts supportsLaura Milišić, Blaž Belec, Anja Siher, Gregor Žerjav, Albin Pintar, Andraž Mavrič, 2025, published scientific conference contribution abstract Keywords: surface acidity, surface basicity, ZnAlGaOx catalysts, layered double hydroxide, pyridine temperature-programmed desorption, TPD
Published in RUNG: 20.03.2025; Views: 1056; Downloads: 3
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10. Inference of the Mass Composition of Cosmic Rays with Energies from 10[sup]18.5 to 10[sup]20 eV Using the Pierre Auger Observatory and Deep LearningA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, original scientific article Abstract: We present measurements of the atmospheric depth of the shower maximum Xmax,
inferred for the first time on an event-by-event level using the Surface Detector
of the Pierre Auger Observatory. Using deep learning, we were able to extend
measurements of the Xmax distributions up to energies of 100 EeV (10[sup]20 eV),
not yet revealed by current measurements, providing new insights into the mass
composition of cosmic rays at extreme energies.
Gaining a 10-fold increase in statistics compared to the Fluorescence Detector data,
we find evidence that the rate of change of the average Xmax with the logarithm
of energy features three breaks at 6.5 ± 0.6 (stat) ± 1 (sys) EeV,
11 ± 2 (stat) ± 1 (sys) EeV, and 31 ± 5 (stat) ± 3 (sys) EeV, in the vicinity to the three
prominent features (ankle, instep, suppression) of the cosmic-ray flux.
The energy evolution of the mean and standard deviation of the measured Xmax
distributions indicates that the mass composition becomes increasingly heavier
and purer, thus being incompatible with a large fraction of light nuclei between
50 EeV and 100 EeV.
Keywords: ultra-high-energy cosmic rays (UHECRs), extensive air showers, Pierre Auger Observatory, UHECR mass composition, depth of the shower maximum, fluorescence detector, surface detector, deep learning
Published in RUNG: 20.01.2025; Views: 956; Downloads: 6
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