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Opis: During almost 20 years of regular data acquisition, the Pierre Auger Observatory, the world's largest facility for measuring ultra-high energy cosmic rays, has collected a vast and diverse amount of data covering complementary research fields from astroparticle and fundamental physics to space weather science. The Pierre Auger Collaboration has embraced the concept of open access to research data since its foundation. Since then, a gradual release process has been initiated, and a dedicated task force has been established to implement and sustain this effort over the long term. In line with the FAIR (Findable, Accessible, Interoperable, and Reusable) principles, the mandate of the task force includes the selection of data samples and the documented translation of in-house analyses codes into popular and available software for easy exploration and manipulation of the data. The Pierre Auger Open Data Portal was launched in February 2021 and contains 10% of the cosmic-ray data and 100% of the atmospheric and space-weather data. Since its initial release, the Portal has been extended and updated with new data samples. It also includes a detailed catalog of the showers created by the highest-energy particles and an outreach section aimed at engaging the general public in cosmic-ray science. The foreseen increase of the fraction of released cosmic-ray data to 30% and the inclusion of new detectors will further boost the scientific community's interest in the Observatory's data and their use for education and outreach initiatives.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, open data, FAIR data principles, the Pierre Auger Open Data Portal
Objavljeno v RUNG: 29.05.2025; Ogledov: 353; Prenosov: 5
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Opis: Ultra-high-energy photons (E ≥ 10[sup]17 eV) are expected as by-products of interactions between ultra-high-energy cosmic rays (UHECRs) and background radiation fields or galactic matter, as well as from decay of super-heavy dark matter. Despite these various production mechanisms, the diffuse photon flux is too low for direct detection. Consequently, photon searches at UHE must rely on large ground-based detector arrays. In this contribution, we present a method for photon-hadron discrimination based on deep learning algorithms applied to detector simulations within the context of the Pierre Auger Observatory. Our method correlates information from the Surface Detector (SD), sensitive to air-shower particles arriving to the ground, and the Underground Muon Detector (UMD), sensitive to muons with energies above ∼ 1 GeV. We chose graph neural networks (GNNs) for their effectiveness in handling the discrimination task, allowing for an easy and flexible correlation of information from the SD and UMD. This approach is particularly suitable for handling the irregular structures found in SD and UMD configurations, where stations may be missing due to technical issues. Using simulations, the performance indicates that the method has strong potential for identifying photons, suffering at most 10[sup]−4 background contamination at 0.5 signal efficiency. Future studies will delve into how much that background contamination can be diminished.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHE photons, extensive air showers, AugerPrime upgrade
Objavljeno v RUNG: 29.05.2025; Ogledov: 335; Prenosov: 4
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Opis: Astrophysical neutral particles, such as neutrons, are produced through interactions of charged cosmic rays in the vicinity of their acceleration sites and are not deflected by magnetic fields during propagation. Therefore, they can be traced back to their sources. Despite being unstable particles, neutrons can travel approximately 9.2 kpc per EeV of energy before decaying, confining the search for their possible sources to the Milky Way. In this study, which was carried out with 19 years of data collected by the Pierre Auger Observatory, we analysed data sets nearly three times larger than those used in previous analyses. We extended the search to declinations up to +45◦ and to lower energy showers by including data sets with reconstructed primary energies down to 0.1 EeV. This extensive, high-quality dataset is studied in correlation with catalogues of over 800 Galactic candidate sources, including the Crab Nebula, which is studied for the first time in this type of analysis. The analysis method we present has been specifically developed for this study, allowing us to establish upper limits on the neutron flux from the sources under investigation.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHE neutrons, Galactic sources, Crab Nebula
Objavljeno v RUNG: 29.05.2025; Ogledov: 312; Prenosov: 4
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Opis: 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.
Ključne besede: ultra-high-energy (UHE) cosmic rays, UHE photons, Pierre Auger Observatory, diffuse photon flux, extensive air showers, water-Cherenkov surface detectors, underground muon detectors
Objavljeno v RUNG: 26.05.2025; Ogledov: 336; Prenosov: 4
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Opis: 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.
Ključne besede: 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
Objavljeno v RUNG: 16.05.2025; Ogledov: 378; Prenosov: 4
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