51. Neural networks for photon searches with AugerPrimeEzequiel Rodriguez, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci 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: 487; Prenosov: 5
 Celotno besedilo (8,68 MB)
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52. Estimation of muons on the surface and correlation with the muonic signal of AugerPrimeCarmina Perez Bertolli, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci Opis: This work focuses on estimating the muon density at ground level using simulations and investigating its correlation with the muonic signal recorded by the Water Cherenkov Detectors (WCDs) of the Pierre Auger Observatory. The study is motivated by the need to validate the estimation of the muonic signal in the WCDs. The methodology involves the development of a parameterization for the surface muon density based on simulated muon data from the Underground Muon Detector (UMD) of AugerPrime—an upgrade to the Pierre Auger Observatory. Our results indicate a negligible bias and a resolution better than 40 at energies above 10[sup]17.5 eV. Furthermore, we find a strong positive correlation between the estimated muon density and the simulated muonic signals in the WCDs.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, extensive air showers, AugerPrime upgrade, muonic air-shower component
Objavljeno v RUNG: 29.05.2025; Ogledov: 487; Prenosov: 7
Celotno besedilo (861,22 KB)
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53. Search for neutrons from Galactic sources with the Pierre Auger ObservatoryMiguel Alexandre Martins, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci 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: 478; Prenosov: 8
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54. Prospects of a composition-enhanced search for large-scale anisotropy with the Pierre Auger ObservatoryEdyvania Emily Martins, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2025, objavljeni znanstveni prispevek na konferenci Opis: The Pierre Auger Observatory has been collecting data for over 19 years, reaching more than 135 000 sq. km yr sr of accumulated exposure, with the surface detectors spread over 3000 sq. km. A remarkable discovery is the large-scale dipole structure with a total amplitude of 7.4% for energies above 8 EeV. The observed modulation in right ascension has a statistical significance of 6.8 sigma. The dipolar pattern in the events with energies between 8 and 16 EeV has a statistical significance of over 5 sigma. The Pierre Auger Collaboration has also reported an increase in the dipole amplitude with energy. This anisotropy is understood to be of extragalactic origin, as the maximum of the dipolar component is located ∼ 115◦ away from the Galactic Center. In the same energy range, the observed evolution of the depth of maximum shower development with energy indicates a progression towards heavier composition of cosmic rays with increasing energy. This contribution presents a novel approach to a search for composition-enhanced large-scale anisotropy. On the one hand, lighter events have higher rigidity than their heavier counterparts with similar energy; therefore, their trajectories are less affected by magnetic fields. The expected effect is a higher anisotropy in the arrival direction of a subset of events with smaller mass and charge than the anisotropy in the overall flux of cosmic rays. On the other hand, the attenuation length is distinct for each mass group, leading to different horizon of cosmic ray sources for each of them. Under a source-agnostic model, we investigate the dipole amplitude as a function of rigidity. Using a simulation library, we analyze the possibility of measuring a separation in total dipole amplitude between two sub-populations distinct in mass of the Auger Phase I dataset.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHECR arrival directions, UHECR mass composition, large-scale anisotropy
Objavljeno v RUNG: 29.05.2025; Ogledov: 408; Prenosov: 3
Celotno besedilo (1,23 MB) |
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